Effects of topoclimatic complexity on the composition of woody plant communities.

Topography can create substantial environmental variation at fine spatial scales. Shaped by slope, aspect, hill-position and elevation, topoclimate heterogeneity may increase ecological diversity, and act as a spatial buffer for vegetation responding to climate change. Strong links have been observed between climate heterogeneity and species diversity at broader scales, but the importance of topoclimate for woody vegetation across small spatial extents merits closer examination.

Topography as a driver of diversification in the Cape Floristic Region of South Africa.

The rugged topography of the Cape Floristic Region (CFR), South Africa, is frequently invoked to explain the spectacular radiation of the Cape flora, but the mechanisms involved remain unclear. Where recent authors emphasize the importance of elevation gradients as stimuli for ecological speciation, earlier workers stressed the role of topography as an isolating mechanism, particularly in montane lineages. Using six Cape plant lineages, we tested whether elevation niches are phylogenetically conserved.

Topography as a driver of cryptic speciation in the high-elevation cape sedge Tetraria triangularis (Boeck.) C. B. Clarke (Cyperaceae: Schoeneae).

Since some speciation mechanisms are more likely to generate morphological disparity than others, the general failure of vascular plant taxonomists to recognize cryptic diversity may bias perceptions about speciation process in plants. While the exceptional floristic richness of the South African Cape has largely been attributed to adaptive divergence ('ecological' speciation), a combination of climatic dynamism and complex topography has likely provided ample opportunities for 'non-ecological' vicariant speciation, a mechanism which is perhaps more likely to produce cryptic species. We explore the role of topography as a driver of 'non-ecological' speciation in the high-elevation sedge Tetraria triangularis.

Ecology limits the diversity of the Cape flora: phylogenetics and diversification of the genus Tetraria.

Understanding the ecology and evolution of the hyper-diverse Cape flora is dependent on developing an understanding of its component parts, best epitomized by the Cape floral clades that have diversified and are largely endemic to the region. Here we employ a new dated phylogenetic hypothesis for the sedge genus Tetraria, one of the smaller Cape floral clades, to develop an understanding of timing and rates of diversification in the group. Specifically, we test whether diversification in Tetraria slowed as the number of extant lineages increased, suggesting that available ecological niche space has become increasingly saturated through time.