The species-rich flora of southern Africa comprises a high number of endemics, including succulents such as the flowering stones in the genus
We wanted to assess plant abundance and identify factors that may affect survival in
Field surveys were carried out in nine populations in Namibia. The most meticulously studied population was divided into 51 sites, while another 43 sites were recognised in the remaining eight populations. At each site, occupied area and number of plants were recorded as well as altitude, aspect, slope, soil texture and substrate. Amplified fragment length polymorphism markers were employed to study 52 individuals from seven populations.
In total, 8465 individuals were recorded. Plant density and/or plant number was associated with aspect, slope, soil texture, substrate and geographic distance from the coast. Analysis of molecular variation showed that 95% of the variability occurs within populations. Genetic and geographic distances among populations were correlated suggesting an isolation-by-distance pattern.
Results are concordant with a strong impact of fog-based precipitation on plant density in the coastal populations, whereas rain probably is more important at one population which is situated further inland. Within-population genetic variation was medium high as usually reported for perennial, outcrossing species, but the low population differentiation implies considerable gene flow and/or population fragmentation.
Southern Africa harbours many endemic leaf succulents because of the unique environmental conditions (Young & Desmet
One of the insufficiently studied succulent genera is
For this study, we focus on
Plants of
Populations of
Genetic variability and processes, such as isolation-by-distance and genetic drift, can be studied by deoxyribonucleic acid (DNA)-based markers, and appear to be closely associated with life form, breeding system, mode of seed dispersal and successional status (Nybom
The current study was undertaken to estimate plant abundance in
Distribution of surveyed
Boundaries are difficult to define for large populations that consist of many small and widely dispersed groups of plants. In this study, a site is defined as a group of plants that grow together on the same topographic feature such as a ridge, outcrop, slope or a gravel plain, and with no plants separated by unsuitable habitat. By contrast, sites within a population can be separated by unsuitable habitat although cross-pollination between sites should still be possible. A population is defined as a group of sites occurring at the same geographic location. Populations are separated by significant distances (minimum 10 km), unsuitable habitat and/or geographic barriers, making inter-populational cross-pollination unlikely. Only one site constitutes the entire population at View Point in the Skeleton Coast Park. For each population, number of sites, plants and occupied area are shown in
Investigated populations with number of sites, number of plants and occupied area.
Population | Sites | Plants | Area (m²) |
---|---|---|---|
Feldspar Ridge | 2 | 307 | 19 362 |
Henties Bay–Uis Road | 11 | 1158 | 66 716 |
Hoanib River | 4 | 1380 | 23 608 |
Khumib River | 6 | 2213 | 16 004 |
Rössing Mountain | 5 | 418 | > 12 033 |
Rössing Uranium Limited (RUL) | 51 | 2008 | > 51 562 |
Ugab River | 12 | 741 | 15 766 |
Ugab Salt Works | 2 | 148 | 8979 |
View Point | 1 | 92 | 500 |
One very large population, RUL, received special attention because of its size and previous plant and habitat analyses. Burke (
In each of the other eight successfully located populations, all
Only one population (Khumib River) contained plants that were identified as var.
Seed capsules were collected from seven populations (
Genetic variation was investigated using standard AFLP procedure (Vos et al.
The numerical plant and habitat parameters (altitude, slope, distance from coast, occupied area, plant number and plant density) were tested for normality using the Anderson Darling test and transformed into natural logarithms as needed. Statistical analyses of plant and habitat parameters were carried out on two separate data sets: (1) sites in the RUL population and (2) sites in the other eight populations. Firstly, the relationships between occupied area, plant number and plant density were estimated by Spearman rank correlation analyses. Subsequently, associations between plant parameters and habitat parameters were estimated using univariate (including all data, i.e. 51 and 43 sites, respectively) and multivariate methods (including only 29 and 26 sites, respectively, because of list-wise deletion of missing values). Spearman rank correlation analyses were performed to study associations between the numerical habitat parameters (altitude, slope and coastal distance) and plant number and plant density. Several one-way analyses of variance (ANOVA) were performed to study the possible impact of category habitat parameters (aspect, substrate and soil texture) on plant number and plant density, followed by Tukey pairwise comparisons. Because of the unbalanced number of sites for especially aspect, some alternatives were merged into wider groups (e.g. NE+N+NW). A general linear mixed model (GLM) was used to analyse the effects of all parameters (altitude, slope, coastal distance, aspect, substrate and soil texture) simultaneously and their interactions as fixed effects, and sites per populations as random effects, on plant density and total plant number. The analyses were performed under the R environment (R Core Team
Principal component analyses (PCAs) were performed to explore the relationships between the habitat parameters, using indicator (dummy) variables for aspect, substrate and soil texture. In addition, plant number and occupied area were entered into the analysis to highlight the co-occurrences (but not the causality) between these parameters and the habitat parameters.
The AFLP data were used to estimate genetic variance within and among populations by an analysis of molecular variance (AMOVA) using GenAlEx v.6.5 (Peakall & Smouse
This article followed all ethical standards for research without direct contact with human or animal subjects.
During the field work in 2006–2008, only nine
A total of 8465
Percentage of mature plants out of the total number was 90.3%, while 8.6% were damaged and 1.1% were juveniles (
As
The survey of the RUL population initially made use of 75 sampling points. While no
In the other eight populations,
The boundaries of a site (i.e. occupied area) were determined by the number of plants as well as the distances between these plants. As expected, positive correlations were obtained between occupied area and number of plants, both in RUL and in the other eight populations (
Spearman rank correlation values for associations among occupied area, plant number and plant density, and two numerical habitat parameters (altitude and slope) at 51 sites in the Rössing Uranium Limited population, and at 43 sites in the other eight populations.
Parameter 1 | Parameter 2 | |||
---|---|---|---|---|
Plant number | Occupied area | 0.585 | 43 | < 0.001 |
Plant number | Plant density | −0.137 | 43 | 0.369 |
Occupied area | Plant density | −0.732 | 43 | < 0.001 |
Plant number | Altitude | 0.084 | 51 | 0.593 |
Plant number | Slope | 0.127 | 42 | 0.454 |
Plant density | Altitude | −0.223 | 43 | 0.150 |
Plant density | Slope | 0.411 | 37 | 0.012 |
Plant number | Occupied area | 0.676 | 41 | < 0.001 |
Plant number | Plant density | 0.418 | 41 | 0.006 |
Occupied area | Plant density | −0.363 | 41 | 0.020 |
Plant number | Altitude | 0.195 | 40 | 0.222 |
Plant number | Slope | 0.445 | 37 | 0.006 |
Plant number | Coastal distance | −0.157 | 43 | 0.314 |
Plant density | Altitude | 0.098 | 39 | 0.546 |
Plant density | Slope | 0.504 | 36 | 0.002 |
Plant density | Coastal distance | −0.308 | 41 | 0.047 |
RUL, Rössing Uranium Limited.
, 0.05 >
, 0.01 >
,
Information about habitat variables for each site is presented in
Principal component analysis showing the relationship between number of plants (Number), occupied area (Area) and habitat parameters: altitude, aspect (N+NE+NW, SW, S+SE+E, LEVEL), gradient (degree of slope), soil texture (loam, light clay, silt loam, clay loam) and substrate (Quartz + other, Granite + other, Schist + other, Feldspar + other) in the 51 sites at Rössing Uranium Limited.
Principal component analysis showing the relationship between number of plants (Number), occupied area (Area) and habitat parameters: altitude, aspect (LEVEL, W, SW, S+SE+E, N+NE+NW), coastal distance, gradient (degree of slope), soil texture (loamy sand, silt loam, sand) and substrate (Quartz + other, Schist + other, Pegmatite + other, Feldspar + other, Granite + other) in the 43 sites of the other eight populations.
At RUL, all sites were found within a range of 527–704 metres above sea level (masl). The steeper sites occurred mostly at the lower altitudes, usually with a southern–eastern aspect, on feldspar, granite or schist, with light clay. Sites at higher altitudes tended to have a northern or western aspect, and were situated mainly on quartz with loam or silt loam. By contrast, altitude varied considerably among the eight populations (18–617 masl), with sites at higher altitudes overall steeper with an eastern–southern–southwestern aspect, an overrepresentation of the substrates feldspar and pegmatite, and silt loam. Sites at lower altitudes instead tended to be level or to have a northern aspect, and to have granite or quartz, and sand or loamy sand. Associations between the habitat parameters and the plant abundance parameters are consistent with the statistical analyses described below.
At RUL, the most common aspect group was S+SE+E (23 sites), while the other aspect groups occurred in only three to six sites each (
Importance of three habitat parameters (aspect, soil texture and substrate) for plant number and plant density determined with analysis of variance and Tukey pairwise comparisons, for 51 sites at Rössing Uranium Limited and for 43 sites at the other eight populations.
Parameter | df | ||
---|---|---|---|
Aspect (Plant number) | 4/33 | 1.41 | 0.251 |
Aspect (Plant density) | 4/29 | 3.34 | 0.022 |
Soil texture (Plant number) | 3/47 | 0.99 | 0.407 |
Soil texture (Plant density) | 3/39 | 1.35 | 0.272 |
Substrate (Plant number) | 3/45 | 0.49 | 0.691 |
Substrate (Plant density) | 3/38 | 0.30 | 0.827 |
Aspect (Plant number) | 4/28 | 3.64 | 0.016 |
Aspect (Plant density) | 4/26 | 3.12 | 0.032 |
Soil texture (Plant number) | 2/40 | 4.00 | 0.026 |
Soil texture (Plant density) | 2/37 | 2.34 | 0.111 |
Substrate (Plant number) | 4/36 | 1.52 | 0.218 |
Substrate (Plant density) | 4/33 | 4.16 | 0.008 |
For an extended version, see
, 0.05 >
, 0.01 >
RUL, Rössing Uranium Limited; df, degrees of freedom.
Factors and co-variables selected by a general linear mixed model to explain variation in plant density and total plant number for 29 sites at Rössing Uranium Limited.
Source of variation | Sum of squares | Mean squares | df | Pr(> |
|
---|---|---|---|---|---|
Aspect | 0.0499 | 0.0125 | 4/15 | 00.29 | 0.8807 |
Soil type | 0.0457 | 0.0152 | 3/15 | 00.35 | 0.7880 |
Substrate | 0.0083 | 0.0028 | 3/15 | 00.06 | 0.9780 |
Soil type: Substrate | 0.2233 | 0.0745 | 3/15 | 01.72 | 0.2051 |
Altitude | 119 | 119 | 1/8 | 00.15 | 0.7072 |
Slope | 548 | 548 | 1/8 | 00.70 | 0.4277 |
Aspect | 35 502 | 8876 | 4/8 | 11.30 | 0.0023 |
Soil type | 1029 | 343 | 3/8 | 00.44 | 0.7327 |
Substrate | 2050 | 683 | 3/8 | 00.87 | 0.4956 |
Altitude: Slope | 610 | 610 | 1/8 | 00.78 | 0.4037 |
Altitude: Aspect | 1428 | 476 | 3/8 | 00.61 | 0.6294 |
Slope: Aspect | 26 143 | 8714 | 3/8 | 11.10 | 0.0032 |
Altitude: Slope: Aspect | 1606 | 1606 | 1/8 | 02.05 | 0.1906 |
df, degrees of freedom.
, 0.01 >
Factors and co-variables selected by a general linear mixed model to explain variation in plant density and total plant number for 26 sites at the other eight populations.
Source of variation | Sum of squares | Mean squares | df | Pr(> |
|
---|---|---|---|---|---|
Altitude | 0.0000 | 0.0000 | 1/0.00 | 34.30 | 0.9999 |
Coastal distance | 0.0005 | 0.0005 | 1/0.00 | 745.89 | 1.0000 |
Soil type | 0.0092 | 0.0046 | 2/2.00 | 7569.77 | 0.0001 |
Substrate | 0.0120 | 0.0030 | 4/2.00 | 4933.73 | 0.0002 |
Aspect | 0.0052 | 0.0013 | 4/2.00 | 2143.36 | 0.0005 |
Slope | 0.0082 | 0.0082 | 1/0.00 | 13 502.79 | 1.0000 |
Soil type: Substrate | 0.0022 | 0.0011 | 2/2.00 | 1836.04 | 0.0005 |
Soil type: Aspect | 0.0012 | 0.0004 | 3/2.00 | 663.83 | 0.0015 |
Substrate: Aspect | 0.0029 | 0.0010 | 3/2.00 | 1592.39 | 0.0006 |
Soil type: Slope | 0.0048 | 0.0048 | 1/0.00 | 7851.67 | 1.0000 |
Substrate: Slope | 0.0027 | 0.0027 | 1/0.00 | 4367.92 | 1.0000 |
Aspect: Slope | 0.0026 | 0.0026 | 1/0.00 | 4259.93 | 1.0000 |
Altitude | 373 | 373.5 | 1/0.70 | 0.1669 | 0.7738 |
Coastal distance | 140 | 139.8 | 1/0.64 | 0.0625 | 0.8593 |
Soil type | 25 166 | 12 582.9 | 2/3.47 | 5.6234 | 0.0815 |
Substrate | 77 027 | 19 256.7 | 4/2.00 | 8.6059 | 0.1068 |
Aspect | 5597 | 1399.3 | 4/2.00 | 0.6254 | 0.6912 |
Slope | 18 965 | 18 965.1 | 1/47.15 | 8.4756 | 0.0055 |
Soil type: Substrate | 8218 | 4108.8 | 2/4.89 | 1.8362 | 0.2541 |
Soil type: Aspect | 13 534 | 4511.2 | 3/2.00 | 2.0161 | 0.3485 |
Substrate: Aspect | 24 999 | 8333.1 | 3/2.00 | 3.7241 | 0.2189 |
Soil type: Slope | 21 597 | 21 596.9 | 1/1979.22 | 9.6518 | 0.0020 |
Substrate: Slope | 3029 | 3028.9 | 1/7.67 | 1.3536 | 0.2796 |
Aspect: Slope | 47 | 46.5 | 1/5.76 | 0.0208 | 0.8903 |
df, degrees of freedom.
, 0.01 >
,
Soil texture differed considerably between the two data sets, with only loamy sand (27 sites), silt loam (nine sites) and sand (seven sites) recorded in the eight populations, whereas clay loam, light clay, loam and silt loam were almost equally common (11–15 sites) at RUL (
The most common substrate at RUL was quartz + other (28 sites) followed by feldspar + other (13 sites) and granite + other (six sites), while quartz + other (17 sites), granite + other (15 sites) and pegmatite + other (four sites) were most common in the eight populations data set (
When instead plant density was used as the dependent variable in ANOVA, aspect had a significant impact both at RUL (
Spearman rank correlation coefficients and GLM were used to detect associations between the two quantitative habitat parameters altitude and slope, on the one hand, and plant number and plant density, on the other hand (
The pH ranged between 7.7 and 9.6 in all the 30 soil samples, indicating that
A total of 52 individuals from seven populations were analysed with four primer pairs yielding 102 polymorphic AFLP bands. Mean percentage of polymorphic loci was 65.97 and mean expected heterozygosity was 0.239 (
Amplified fragment length polymorphism (AFLP)-based estimates of genetic variation, within each of the seven sampled
Population | Number of plants | PPL | |
---|---|---|---|
Rössing Uranium Mine (RUL) | 6 | 60.78 | 0.221 |
Khumib River | 7 | 75.49 | 0.279 |
Ugab River | 6 | 53.92 | 0.199 |
Feldspar Ridge | 7 | 68.63 | 0.253 |
Rössing Mountain | 8 | 73.53 | 0.260 |
Henties Bay–Uis Road | 9 | 64.71 | 0.216 |
Henties Bay–Usakos Road | 9 | 64.71 | 0.244 |
PPL, percentage of polymorphic loci; RUL, Rössing Uranium Limited.
Distribution of molecular variance among and within seven populations and six populations (without Khumib River) of
Source of variation | df | Sum of squares | Estimated variance | Percentage of variance |
---|---|---|---|---|
Among populations | 6 | 120.2 | 0.80 | 5 |
Within populations | 45 | 635.6 | 14.12 | 95 |
Among populations | 5 | 86.0 | 0.46 | 3 |
Within populations | 39 | 536.1 | 13.74 | 97 |
df, degrees of freedom.
The Mantel test showed a correlation between geographic and genetic distances (
The PCoA is a multivariate test that reveals amount of similarity among samples without presuming any group structure. The first three dimensions explained a total of 30.3% of the variance when all samples were analysed together, and showed that the Khumib River samples are widely dispersed and that many occur as outliers in the right hand and lower parts of the plots (
Principal coordinate analysis of amplified fragment length polymorphism data for 52 plants derived from seven populations of
In the largest and most detailed field inventory ever published on a single
The main reasons that only nine out of the 21 recorded populations were located are probably: (1) locality descriptions on herbarium specimens and in publications lack sufficient detail or are deliberately vague so as to prevent illegal collecting, and (2) the cryptic nature of the plants: in the absence of rain for a prolonged period of time, plants shrink and become concealed by their substrate. Despite spending hours looking for the population near Cape Cross, for example, we were unable to find it although it was subsequently located (Jainta
Because of the clumped distribution of plants within a population, previous attempts to apply plant density estimation methods in
A clumped distribution has been described for many species in the family Aizoaceae (Burke & Mannheimer
Fog has a crucial impact on all vegetation in the Namib desert. The high fog zone extends up to 60 km inland from the Atlantic Ocean and produces fog-derived precipitation 60–120 days per year (Mendelsohn et al.
Although it takes rainfall events to trigger germination and initial establishment of
Estimation of plant abundance is not straightforward in species with a patchy or heavily clumped distribution. Plant number and occupied area provide different estimates of the size of a plant site, but plant density was more closely associated with most of the habitat variables and therefore appears to be superior for determination of habitat preferences. It should also be stressed that the associations reported in this study are tentative only, as a larger set of more balanced data is needed for exploration of the true magnitude of impact from each habitat parameter.
Altitude most likely affects the ability of the sites to retain fog precipitation, but the range was very small at RUL (527–704 m) and no associations were found. The larger range recorded in the eight populations data set (18–617 m) possibly helped to detect a positive association with plant number as indicated in the PCA (
Slope ranged from 0° to 40° at RUL and between 0° and 25° in the eight populations. In the latter data set, positive correlations were found between slope, on the one hand, and plant number and density, on the other hand. These associations are most likely because of an increased interception of fog precipitation at the steeper slopes found on inselbergs and rocky ridges. Interestingly, some of the largest and densest populations were found on overall steeper terrain, such as Khumib River, Hoanib River, Rössing Mountain and Feldspar Ridge. As RUL is located further inland, steeper slopes will not have the same beneficial effect. The weaker but still significant positive correlation between plant density and slope at RUL would instead be because the hilly terrain harbours overall smaller sites with high plant densities. By contrast, the level terrain at RUL consists of gravel plains interrupted by dry sandy water courses and holds fewer plants albeit often on large surfaces.
Distance from the coast may have an impact on plant abundance, given that fog-derived precipitation plays an important role although surface winds, carrying fog from the ocean, as well as the often variable mountain-plain winds, should not be underestimated (Seely & Henschel
Aspect had considerable influence, with plant number being the highest on SW-facing slopes in the eight populations. SW- and S–E-facing slopes also harboured sites with the highest density in both data sets. The beneficial impact of SW-facing slopes is consistent with the fog arriving with coastal winds (Seely & Henschel 1988). In the putatively less fog-dependent RUL population, the majority of the analysed sites were, however, found on S–E-facing slopes. In Namibia, rain usually arrives with eastern winds, and the rain-dependent
Substrate had no significant impact on plant number or density at RUL, while a positive influence was demonstrated in the eight populations with pegmatite+other doing best. Moreover, most of the
An impact of soil texture was noted only in the eight populations where silt loam appears to be more beneficial than sandy loam or sand. Sand had a negative impact also on
Amplified fragment length polymorphism markers have been used to successfully investigate differentiation at population level of species in the sub-family Ruschioideae (Buys et al.
Within-population diversity estimated as expected heterozygosity had a mean of 0.24, which is similar to previously reported values and also in keeping with random amplified polymorphism DNA (RAPD)-derived estimates for short-lived perennials (0.20), with narrow-range distribution (0.28), outcrossing breeding system (0.27), water-dispersed seeds (0.27) and growing in early-successional vegetation (0.17; Nybom
Only 5% of the genetic variability occurred among populations, indicating very low differentiation.
In the assessment for the Red Data Book (Loots
Number of juveniles is likely to be grossly underestimated, and recruitment probably takes place in most populations. Witkowski and Liston (
The current status of Least Concern remains valid for
Results are concordant with a strong impact of fog-based precipitation on especially plant density in populations closer to the coast, whereas rain is probably more important at RUL which is situated further inland. Within-population genetic variation was medium high but the low population differentiation implies considerable gene flow and/or recent population fragmentation and holds clues for a conservation strategy for the species.
J.-E. Englund is thanked for statistical help, M. Fatih for logistical support in Sweden and the staff of the Senckenberg BIK-F laboratory (Frankfurt am Main, Germany) for technical support in AFLP analyses. Financial support was received from Rio Tinto, RBG Kew, Rössing Uranium Limited, MAWF and Sida (Swedish International Development Cooperation Agency) as part of Nordic support to SADC Plant Genetic Resources Project. Staff of the National Botanical Research Institute assisted with field work and logistical support.
The authors declare that they have no financial or personal relationships that may have influenced them in writing this article.
S.L. designed the study, performed the field work and most of the statistical evaluations, carried out most of the laboratory work and had a leading role in writing this manuscript. C.M.R. supervised the laboratory work, performed the AFLP data evaluations and contributed to this manuscript. M.S. assisted with the laboratory work. J.S. performed the AFLP band scoring. V.H. conducted some of the statistical analyses. L.G.-G. contributed to this manuscript. H.E.N. supervised the study and assisted in writing this manuscript.
Rio Tinto, Rössing Uranium Limited, MAWF and SADC Plant Genetic Resources Centre (SPGRC) and Sida (Swedish International Development Cooperation Agency) as part of the Nordic support to the SADC Plant Genetic Resources Project. Senckenberg BIK-F laboratory (Frankfurt am Main, Germany) provided technical support for AFLP analyses.
Data created during this study belong to the Government of Namibia and the authors. Data sharing is possible with the application of information request forms, available on the website of the National Botanical Research Institute of Namibia (
The views expressed in the submitted article are our own, and do not represent anyone else.
Field data, including habitat parameters, plant number, occupied area and plant density, collected for 51
Site | Altitude (masl) | Soil texture | Substrate | Aspect | Slope | Mature plants | Damaged plants | Juveniles | Total number of plants | Occupied area (m²) | Density (number of plants/occupied area) |
---|---|---|---|---|---|---|---|---|---|---|---|
1 | 648 | light clay | feldspar, granite | S, W, E / undetermined* | 7.0 | 136 | 40 | 6 | 182 | 6355 | 0.029 |
2 | 672 | loam | quartz | S, W, E, N / undetermined | 1.0 | 144 | 31 | 3 | 178 | 12000 | 0.015 |
3 | 632 | clay loam | quartz, schist, feldspar | E, S / grouped with S+SE+E | 1.0 | 21 | 1 | 0 | 22 | 1384 | 0.016 |
4 | 594 | loamy sand | quartz, feldspar | S, W, E, N / undetermined | 5.0 | 19 | 19 | 0 | 38 | 1555 | 0.024 |
5 a | 633 | silt loam | granite | level | 0.0 | 42 | 11 | 0 | 53 | 1500 | 0.035 |
5 b | 636 | not recorded | not recorded | S, W, E, N / undetermined | 2.3 | 38 | 4 | 2 | 44 | 340 | 0.129 |
6 a | 612 | silt loam | quartz, feldspar | not recorded | not recorded | 11 | 1 | 0 | 12 | 1371 | 0.009 |
6 b | 681 | not recorded | quartz, feldspar | not recorded | not recorded | 15 | 5 | 0 | 20 | not measured | |
6 c | 647 | not recorded | quartz, feldspar | not recorded | not recorded | 18 | 6 | 0 | 24 | not measured | |
6 d | 618 | not recorded | quartz, feldspar, granite | level, N, SW, W / undetermined | 7.2 | 40 | 11 | 0 | 51 | not measured | |
7 | 664 | light clay | granite | SW | 10.5 | 20 | 3 | 2 | 25 | 952 | 0.026 |
8 | 669 | clay loam | quartz, feldspar | W, SW / grouped with W | 20.0 | 54 | 10 | 0 | 64 | 1097 | 0.058 |
9a | 635 | loam | quartz, feldspar | SE | 13.0 | 4 | 1 | 0 | 5 | 10 | 0.500 |
9 b | 639 | not recorded | quartz, feldspar | SE | 10.0 | 7 | 2 | 0 | 9 | 60 | 0.150 |
9 c | 641 | not recorded | quartz, feldspar | SE | 13.0 | 5 | 3 | 0 | 8 | 10 | 0.800 |
9 d | 636 | not recorded | quartz, feldspar | S | 18.0 | 33 | 9 | 0 | 42 | 120 | 0.350 |
10 | 667 | light clay | quartz, feldspar | SW, SE, W / undetermined | 3.0 | 21 | 3 | 0 | 24 | 817 | 0.029 |
11 | 682 | light clay | quartz, feldspar | NW, SE / undetermined | 3.0 | 3 | 3 | 0 | 6 | 1785 | 0.003 |
12 | 679 | clay loam | quartz, feldspar | S | 10.0 | 6 | 1 | 0 | 7 | 525 | 0.013 |
13 a | 700 | clay loam | quartz, feldspar | W | 7.0 | 5 | 2 | 0 | 7 | 948 | 0.007 |
13 b | 704 | not recorded | quartz, feldspar | E | 8.0 | 31 | 11 | 0 | 42 | 453 | 0.093 |
14 | 623 | silt loam | quartz | W | 6.0 | 8 | 0 | 0 | 8 | 1102 | 0.007 |
15 a | 611 | clay loam | quartz, feldspar | S | not recorded | 15 | 2 | 0 | 17 | 130 | 0.131 |
15 b | 619 | not recorded | quartz, feldspar | E | 6.0 | 35 | 4 | 0 | 39 | not measured | |
15 c | 620 | not recorded | quartz, feldspar | S | 9.0 | 10 | 3 | 0 | 13 | 253 | 0.051 |
16 | 624 | clay loam | quartz, feldspar | S | 4.0 | 1 | 0 | 0 | 1 | not measured | |
17 a | 611 | clay loam | feldspar | S, E / grouped with S+SE+E | 14.0 | 78 | 19 | 0 | 97 | 495 | 0.196 |
17 b | 612 | not recorded | feldspar, quartz | S | 20.0 | 5 | 1 | 0 | 6 | 200 | 0.030 |
17 c | 609 | clay loam | quartz, feldspar | W | 14. | 5 | 0 | 0 | 5 | 200 | 0.025 |
17 d | 606 | not recorded | quartz, granite | SE | 3.0 | 3 | 0 | 0 | 3 | not measured | |
18 a | 578 | light clay | feldspar | S | 15.0 | 4 | 7 | 0 | 11 | 1059 | 0.010 |
18 b | 573 | not recorded | feldspar | S | 17.5 | 23 | 1 | 0 | 24 | 500 | 0.048 |
18 c | 577 | not recorded | feldspar | level | 0.0 | 5 | 1 | 0 | 6 | 400 | 0.015 |
18 d | 567 | not recorded | feldspar | E | 10.0 | 5 | 2 | 0 | 7 | 10 | 0.700 |
19 a | 556 | silt loam | feldspar | S, SE, SW / grouped with S+SE+E | not recorded | 32 | 4 | 0 | 36 | 100 | 0.360 |
19 b | 560 | not recorded | feldspar | not recorded | not recorded | 19 | 1 | 0 | 20 | not measured | |
19 c | 560 | not recorded | feldspar | not recorded | not recorded | 12 | 0 | 0 | 12 | 500 | 0.024 |
19 d | 561 | not recorded | feldspar | not recorded | not recorded | 9 | 0 | 0 | 9 | 200 | 0.045 |
20 | 588 | light clay | schist | W | not recorded | 10 | 1 | 0 | 11 | 232 | 0.047 |
21 | 562 | loam | quartz, granite, feldspar | S | 35.0 | 43 | 2 | 0 | 45 | 2135 | 0.021 |
22 | 546 | light clay | schist, quartz, feldspar | S | 25.0 | 32 | 1 | 0 | 33 | 327 | 0.101 |
41 | 652 | loam | marble | SW | 5.0 | 7 | 1 | 0 | 8 | 170 | 0.047 |
44 | 542 | clay loam | not recorded | S | 3.0 | 1 | 0 | 0 | 1 | not measured | |
45 | 527 | clay loam | granite | SW | 20.0 | 4 | 0 | 0 | 4 | 10 | 0.400 |
46 | 657 | light clay | quartz | NW | 10.0 | 9 | 4 | 0 | 13 | 852 | 0.015 |
47 | 608 | loam | granite | SW | 7.0 | 10 | 6 | 0 | 16 | 100 | 0.160 |
48 a | 693 | loam | quartz, feldspar | N, S / grouped with N+NE+NW | 6.5 | 6 | 0 | 0 | 6 | 200 | 0.030 |
48 b | 703 | not recorded | quartz, feldspar | E | 4.0 | 42 | 18 | 0 | 60 | 340 | 0.177 |
49 | 608 | light clay | feldspar | level, S / grouped with level | 15 | 383 | 57 | 0 | 440 | 6676 | 0.066 |
50 | 630 | light clay | feldspar | SE | 7.5 | 39 | 17 | 0 | 56 | 3016 | 0.019 |
68 | 599 | clay loam | quartz, feldspar | SW | 20.0 | 137 | 0 | 0 | 137 | 1073 | 0.128 |
Field data, including habitat parameters, plant number, occupied area and plant density, collected for 43
Site | Altitude (masl) | Coastal distance (km) | Soil texture | Substrate | Aspect | Slope | Mature plants | Damaged plants | Juveniles | Total number of plants | Occupied area (m²) | Density (number of plants /occupied area) |
---|---|---|---|---|---|---|---|---|---|---|---|---|
51 a | 492 | 35.0 | loamy sand | quartz | W | 5 | 26 | 0 | 0 | 26 | 1470 | 0.018 |
51 b | 617 | 35.0 | loamy sand | schist | W | 25 | 168 | 0 | 2 | 170 | 1233 | 0.138 |
51 c | 592 | 34.7 | loamy sand | quartz, schist | not recorded | 12.5 | 142 | 1 | 1 | 144 | 9130 | 0.016 |
51 d | 617 | 35.1 | loamy sand | quartz | W | 12.5 | 71 | 0 | 0 | 71 | not measured | |
51 e | 604 | 33.5 | loamy sand | schist, quartz | not recorded | not recorded | 7 | 0 | 0 | 7 | 200 | 0.035 |
52 a | 470 | 42.7 | silt loam | feldspar, granite, quartz | SW | 15 | 208 | 0 | 0 | 208 | 10154 | 0.021 |
52 b | 470 | 44.2 | silt loam | feldspar, granite | S | 20 | 98 | 0 | 1 | 99 | 9208 | 0.110 |
53 a | 18 | 4.6 | loamy sand | quartz, pegmatite | NW, W / grouped with N+NE+NW | 8 | 72 | 0 | 0 | 72 | 5712 | 0.013 |
53 b | 18 | 4.8 | sand | quartz, pegmatite | level | 2.5 | 76 | 0 | 0 | 76 | 3267 | 0.023 |
83 a | 133 | 26.5 | sand | granite | N | 20 | 7 | 0 | 0 | 7 | 200 | 0.035 |
83 b | not recorded | 26.5 | loamy sand | granite, shale | not recorded | not recorded | 2 | 0 | 0 | 2 | not measured | |
84 a | 103 | 26.2 | loamy sand | granite | NE | 18 | 83 | 0 | 0 | 83 | 1339 | 0.062 |
84 b | 105 | 26.2 | sand | granite, shale | W | 11 | 61 | 1 | 1 | 63 | 439 | 0.144 |
84 c | 110 | 26.2 | loamy sand | granite | not recorded | not recorded | 123 | 1 | 5 | 129 | 5278 | 0.024 |
84 d | 108 | 26.2 | sand | not recorded | W | 10 | 33 | 6 | 0 | 39 | 1272 | 0.031 |
85 a | 100 | 26.8 | loamy sand | granite, shale | SW | 10 | 69 | 1 | 1 | 71 | 1144 | 0.062 |
85 b | 97 | 26.8 | loamy sand | granite, shale | SE | 10 | 161 | 0 | 0 | 161 | 3290 | 0.049 |
86 a | 99 | 26.1 | loamy sand | granite, shale | level | 0 | 8 | 0 | 0 | 8 | 200 | 0.040 |
86 b | 105 | 26.1 | sand | granite, shale | SE | 5 | 4 | 0 | 0 | 4 | 200 | 0.020 |
87 a | 103 | 26.4 | sand | granite, shale | SE | 15 | 113 | 0 | 0 | 113 | 607 | 0.186 |
87 b | 108 | 26.4 | loamy sand | granite, shale | All / undetermined* | 12.5 | 60 | 1 | 0 | 61 | 1797 | 0.034 |
88 a | 180 | 35.0 | loamy sand | quartz, feldspar, others | W | 5 | 65 | 0 | 0 | 65 | 7160 | 0.009 |
88 b | 177 | 35.0 | loamy sand | quartz, feldspar, others | NE | 8 | 20 | 1 | 0 | 21 | 11068 | 0.002 |
89 | 190 | 44.1 | loamy sand | quartz, feldspar, pegmatite | level | 0 | 151 | 5 | 0 | 156 | 22684 | 0.007 |
90 | 201 | 34.1 | loamy sand | quartz, feldspar | All / undetermined | 5 | 139 | 1 | 0 | 140 | 8840 | 0.016 |
91 | 203 | 36.3 | loamy sand | quartz, feldspar | All / undetermined | 10 | 586 | 32 | 3 | 621 | 13729 | 0.045 |
92 a | 309 | 50.9 | loamy sand | quartz | All / undetermined | 5 | 20 | 1 | 0 | 21 | 200 | 0.105 |
92 b | 305 | 50.9 | loamy sand | quartz | All / undetermined | 5 | 5 | 0 | 0 | 5 | 200 | 0.025 |
93 | 320 | 41.48 | loamy sand | quartz, others | level | 0 | 9 | 0 | 0 | 9 | 1185 | 0.008 |
94 a | 228 | 38.0 | loamy sand | quartz, feldspar | N | 16 | 5 | 0 | 0 | 5 | 200 | 0.025 |
94 b | not recorded | 38.0 | loamy sand | quartz, feldspar | not recorded | not recorded | 8 | 0 | 0 | 8 | 200 | 0.040 |
95 | 217 | 37.8 | loamy sand | quartz | level, SW / grouped with level | 2.5 | 103 | 3 | 1 | 107 | 1250 | 0.086 |
96 a | 343 | 26.5 | silt loam | pegmatite, granite, schist | SE, SW / grouped with SW | 17.5 | 641 | 19 | 32 | 692 | 4738 | 0.146 |
96 b | 368 | 26.3 | silt loam | granite, schist, pegmatite, feldspar | SE | 15 | 120 | 7 | 6 | 133 | 1118 | 0.119 |
96 c | 383 | 26.4 | silt loam | not recorded | SE | 13 | 359 | 6 | 13 | 378 | 1815 | 0.208 |
96 d | 325 | 26.4 | silt loam | pegmatite, granite, schist | SE, SW / grouped with S+SE+E | 17.5 | 468 | 1 | 24 | 493 | 4247 | 0.116 |
96 e | 378 | 26.5 | silt loam | pegmatite, schist, granite | SW | 18 | 436 | 2 | 30 | 468 | 1766 | 0.265 |
96 f | 371 | 26.4 | silt loam | pegmatite | NW | not recorded | 47 | 1 | 1 | 49 | 2320 | 0.021 |
97 | 242 | 14.5 | silt loam | quartz, basalt | SW | 15 | 41 | 51 | 0 | 92 | 500 | 0.184 |
98 a | 221 | 18.8 | loamy sand | schist, shale, feldspar, pegmatite, granite | SW | 18 | 283 | 51 | 12 | 346 | 6314 | 0.055 |
98 b | 222 | 18.6 | loamy sand | granite, pegmatite, schist | W | not recorded | 53 | 2 | 1 | 56 | 751 | 0.075 |
98 c | 233 | 18.6 | loamy sand | granite, pegmatite, schist | SW | 25 | 442 | 33 | 14 | 489 | 4146 | 0.118 |
98 d | 225 | 18.8 | loamy sand | granite, pegmatite | W | 10.5 | 455 | 19 | 15 | 489 | 12397 | 0.039 |
Details of ANOVAs performed to investigate the effect of aspect, substrate and soil texture on plant number and density at RUL and the other 8 populations, accompanied by Tukey test grouping (TTG): entries with identical letters do not differ at
Parameter | Categories | Mean | DF | TTG | |||
---|---|---|---|---|---|---|---|
Aspect (Number) | level | 3 | 4.0 | 4/33 | 1.41 | 0.251 | A |
SW | 6 | 3.1 | A | ||||
S+SE+E | 23 | 2.7 | A | ||||
NE+N+NW | 3 | 2.1 | A | ||||
W | 4 | 2.0 | A | ||||
Aspect (Density) | SW | 6 | −2.4 | 4/29 | 3.34 | 0.022 | A |
S+SE+E | 19 | −2.4 | A | ||||
level | 3 | −3.4 | A | ||||
W | 4 | −4.1 | A | ||||
NE+N+NW | 3 | −4.5 | A | ||||
Substrate (Number) | feldspar + other | 13 | 3.3 | 3/45 | 0.49 | 0.691 | A |
granite + other | 6 | 3.2 | A | ||||
schist + other | 2 | 3.0 | A | ||||
quartz + other | 28 | 2.8 | A | ||||
Substrate (Density) | granite + other | 6 | −2.6 | 3/38 | 0.30 | 0.827 | A |
schist + other | 2 | −2.7 | A | ||||
feldspar + other | 12 | −3.0 | A | ||||
quartz + other | 22 | −3.2 | A | ||||
Soil texture (Number) | light clay | 14 | 3.2 | 3/47 | 0.99 | 0.407 | A |
silt loam | 11 | 3.1 | A | ||||
loam | 11 | 3.0 | A | ||||
clay loam | 15 | 2.4 | A | ||||
Soil texture (Density) | loam | 11 | −2.3 | 3/39 | 1.35 | 0.272 | A |
clay loam | 11 | −3.0 | A | ||||
silt loam | 7 | −3.3 | A | ||||
light clay | 14 | −3.4 | A | ||||
Aspect (Number) | SW | 7 | 2.4 | 4/28 | 3.64 | 0.016 | A |
S+SE+E | 7 | 2.0 | A | ||||
W | 8 | 1.9 | A | ||||
level | 5 | 1.6 | A | ||||
NE+N+NW | 6 | 1.4 | A | ||||
Aspect (Density) | SW | 7 | −2.4 | 4/26 | 3.12 | 0.032 | A |
S+SE+E | 6 | −2.5 | A | ||||
W | 7 | −3.1 | A | ||||
level | 5 | −3.9 | A | ||||
NE+N+NW | 6 | −4.1 | A | ||||
Substrate (Number) | pegmatite + other | 4 | 2.5 | 4/36 | 1.52 | 0.218 | A |
feldspar + other | 2 | 2.2 | A | ||||
schist + other | 3 | 1.9 | A | ||||
granite + other | 15 | 1.7 | A | ||||
quartz + other | 17 | 1.7 | A | ||||
Substrate (Density) | pegmatite + other | 4 | −2.3 | 4/33 | 4.16 | 0.008 | A |
schist + other | 3 | −2.7 | AB | ||||
granite + other | 13 | −2.8 | A | ||||
quartz + other | 16 | −3.8 | B | ||||
feldspar + other | 2 | −4.2 | AB | ||||
Soil texture (Number) | silt loam | 9 | 2.3 | 2/40 | 4.00 | 0.026 | A |
loamy sand | 27 | 1.7 | B | ||||
sand | 7 | 1.6 | AB | ||||
Soil texture (Density) | silt loam | 9 | −2.6 | 2/37 | 2.34 | 0.111 | A |
sand | 6 | −3.2 | A | ||||
loamy sand | 25 | −3.5 | A |