High species diversity and turnover in granite inselberg floras highlight the need for a conservation strategy protecting many outcrops

Abstract

Determining patterns of plant diversity on granite inselbergs is an important task for conservation biogeography due to mounting threats. However, beyond the tropics there are relatively few quantitative studies of floristic diversity, or consideration of these patterns and their environmental, biogeographic, and historical correlates for conservation. We sought to contribute broader understanding of global patterns of species diversity on granite inselbergs and inform biodiversity conservation in the globally significant Southwest Australian Floristic Region (SWAFR). We surveyed floristics from 16 inselbergs (478 plots) across the climate gradient of the SWAFR stratified into three major habitats on each outcrop. We recorded 1,060 species from 92 families. At the plot level, local soil and topographic variables affecting aridity were correlated with species richness in herbaceous (HO) and woody vegetation (WO) of soil‐filled depressions, but not in woody vegetation on deeper soils at the base of outcrops (WOB). At the outcrop level, bioclimatic variables affecting aridity were correlated with species richness in two habitats (WO and WOB) but, contrary to predictions from island biogeography, were not correlated with inselberg area and isolation in any of the three habitats. Species turnover in each of the three habitats was also influenced by aridity, being correlated with bioclimatic variables and with interplot geographic distance, and for HO and WO habitats with local site variables. At the outcrop level, species replacement was the dominant component of species turnover in each of the three habitats, consistent with expectations for long‐term stable landscapes. Our results therefore highlight high species diversity and turnover associated with granite outcrop flora. Hence, effective conservation strategies will need to focus on protecting multiple inselbergs across the entire climate gradient of the region.

Contrasting patterns of local adaptation along climatic gradients between a sympatric parasitic and autotrophic tree species

“…These procedures were run separately for each data set and only significant bioclimatic variables were retained. The three spline coefficients were summed for each remaining predictor variable (e.g., subset of geographical distance and the seven climatic variables) to quantify the relative importance (Fitzpatrick et al., 2013; Yates et al., 2019).…”

“…To evaluate the contributions of temperature and precipitation, as captured by multiple climatic variables, and geographical distance in explaining allelic turnover in the model, we partitioned the deviance resulting from GDMs using geographical distance, all significant temperature variables and/or all significant precipitation variables (Borcard et al., 1992; Yates et al., 2019). The partioned deviance values were plotted in Venn diagrams using the R package eulerr version 6.0.0 (Larsson, 2019).…”

Multi‐scale biogeographic controls over plant communities on granite outcrops in the Southwest Australian Floristic Region

“…As far as we are aware, this is one of few studies on biogeographic controls over plant community composition on granite outcrop soil‐patches in the SWAFR (Yates et al . 2019). In general, the clear biogeographic patterns found on rock outcrops in other continents (e.g.…”

“…As we have found clear differences in floristic composition between nearby outcrops, we conclude that protecting multiple outcrops within similar climate gradients is necessary to best facilitate the ongoing persistence of biodiversity across this region (Yates et al . 2019).…”

Variations in floristic composition and community structure between disturbed and undisturbed lowland forest in Aklan, Philippines

“…This information would ensure environmental managers on accurate assessments of possible impacts and amelioration of degraded forest ecosystem (Borah et al, 2014). More so, floristic surveys help in proper monitoring and developing of effective conservation strategies (Alsherif & Fadl, 2016;Yates et al, 2019) for many highly threatened or endangered plant species. However, quantitative studies on plant inventories for the Philippines are still relatively scarce since majority of the plant surveys conducted for the country during the last years are concerted on qualitative species listings (see Ordas et al, 2019;Santiago & Buot, 2017;Villanueva & Buot, 2015) .…”