Evolution of geographical place and niche space: Patterns of diversification in the North American sedge (Cyperaceae) flora

Abstract

The role of geography and ecology in speciation are often discussed in the context of phylogenetic niche conservatism (PNC), the propensity of lineages to retain ancestral niche related traits. However, a recent paradigm shift focuses instead on measuring divergence of these traits in conjunction with patterns of speciation. Under this framework, we analyzed the diversification of North America's third most diverse family, Cyperaceae ("sedges"), using a modified Parsimony Analysis of Endemicity approach to identify floristic regions and ordination statistics to quantify species distribution in a continuous manner. Utilizing over 200,000 georeferenced specimens, we characterized the geographical distribution and climatic and edaphic niche space occupied by each species. We constructed a supermatrix phylogeny of the North American sedge flora, aided in part by the sequencing of all sedges of Wisconsin, and employed a multifaceted approach to assess the role of geographical and ecological divergence on lineage diversification. In addition to measuring phylogenetic signal for these traits, we also measured pairwise phylogenetic distance of species within floristic regions, calculated rates of speciation, and tested for correlations of speciation rate to tempo of geographical and ecological evolution. Our analyses consistently show that evolutionarily related species tend to be geographically unrelated. Rates of geographical and ecological diversification are closely linked to tempo of speciation, and exploration of geographical place coincides with divergence in ecological niche space. We highlight the benefits of treating geography in a continuous manner, and stress the importance of employing a diverse suite of analytical approaches in testing hypotheses regarding the evolution of range and niche.

Biogeography of the cosmopolitan sedges (Cyperaceae) and the area‐richness correlation in plants

“…We suggest, however, that the area-richness correlation observed among angiosperm families (Vamosi & Vamosi, 2011) should be revisited from this ecological perspective. While these results would be strengthened by sister-species comparisons of range and niche on a global scale, they corroborate a recent analysis of the North American sedge flora, which had over 75% complete sampling and found very close correlations of speciation rate with the rates of range and climatic niche evolution (Spalink et al, 2016). While these results would be strengthened by sister-species comparisons of range and niche on a global scale, they corroborate a recent analysis of the North American sedge flora, which had over 75% complete sampling and found very close correlations of speciation rate with the rates of range and climatic niche evolution (Spalink et al, 2016).…”

“…The chromosomal lability of Carex, the multiple origins of C 4 photosynthesis in tribes Abildgaardieae and Cypereae, and the invasion of high latitudes by the DSC clades are also surely involved (Escudero et al, 2012;Bouchenak-Khelladi et al, 2014;Spalink et al, 2016). We established South America as the museum of sedge diversification, present an ancestral area estimation that invokes dispersal as the mechanism by which the sedges have covered the globe, and demonstrate that high temperate diversity is explained by two non-tropical cradles.…”

“…As public databases are useful but prone to error (Maldonado et al, 2015;Spalink et al, 2016), we subjected our waypoint data set to a series of rigorous filtering steps. We mined the Global Biodiversity Information Facility (GBIF; www.gbif.org) and downloaded all georeferenced samples recorded as having no known coordinate ambiguities (accessed 3 November 2015).…”

A tale of worldwide success: Behind the scenes of Carex (Cyperaceae) biogeography and diversification

“…As in other studies (Berger et al, ; Dupin et al, ; Spalink et al, 2016a, 2016b; Zuloaga et al, ), the real importance of allopatric speciation can be masked by these facts, and thus caution should be taken in interpreting our results, that suggest within‐area speciation, but not sympatric speciation in the strict sense, as predominant in Carex . Biogeographic analyses focusing on particular clades and implementing a fine‐scale geographic division within the wide areas considered here would probably unveil a greater role of allopatric speciation processes (i.e., founder events; Spalink et al, ; Johnson et al, ).…”

Pliocene–Pleistocene ecological niche evolution shapes the phylogeography of a Mediterranean plant group

“…The assumption of niche conservatism has recently been further challenged based on examples of rapid niche shifts during species diversification (Evans, Smith, Flynn, & Donoghue, ). Only niche shift allows species to colonize and adapt to new habitats ecologically dissimilar from those on their ancestral areas (Spalink et al., ), or persist in the same area after an environmental change. There is also evidence of niche shifts derived from biological invasions (Broennimann et al., ; Stiels, Gaißer, Schidelko, Engler, & Rödder, ).…”