Niche evolution across spatial scales: climate and habitat specialization in California Lasthenia (Asteraceae)

Abstract

Abstract. Ecologists and evolutionary biologists perceive the ecological niche as a multidimensional relationship between an organism and its environment. Yet, we know little about the degree to which multiple niche axes evolve in concert across various spatial scales to explain differences in distribution patterns and habitat specialization among lineages. Here we used contemporary phylogenetic approaches to analyze the evolution of species' distributions across multiple spatial scales in Lasthenia, a young and ecologically diverse plant clade largely occurring within the California Floristic Province, USA. Lasthenia species and subspecies range from widely distributed taxa that occupy a diversity of habitat types to locally restricted habitat endemics, including several lineages that are strongly associated with isolated ephemeral wetlands called vernal pools. We quantified the niche of Lasthenia species and subspecies at three different spatial scales: the range-wide climate niche, the habitat niche, and the within-habitat depth niche for those taxa occupying vernal pools. We incorporated phylogenetic uncertainty into our analyses by reanalyzing previously described DNA sequences in a Bayesian context and conducting all subsequent comparative analyses over the resulting posterior distribution of ultrametric phylogenetic trees. Using a biogeographic approach for ancestral habitat reconstruction, we estimated that Lasthenia lineages have undergone up to four independent transitions from strictly terrestrial habitats to a niche that incorporates semiaquatic habitats, and one of these transitions led to the subsequent proliferation of vernal pool species and subspecies. We found that the local niche axis, corresponding to the depth distribution of taxa within pools, was more phylogenetically conserved than the large-scale axes representing climatic associations. Furthermore, we did not find evidence that niche breadth estimates along different axes were consistently correlated, indicating that ecological specialization may be specific to certain niche axes rather than an overall characteristic of a species.

Origins of Plant Diversity in the California Floristic Province

“…Vertical zonation of individual pools is often evident from concentric bands of different herbaceous taxa associated with distinct soil conditions that have been shown to represent distinct niche space (e.g., Emery et al 2009). Phylogenetic analysis of different niche components in Lasthenia indicated that the vernal pool depth niche was more evolutionarily conservative than the climate niche; that is, dispersal between pool systems in different climatic regions was more commonly associated with diversification than ecological shifts in pool zonation (Emery et al 2012). Diversification in vernal pools has been associated with increasing specialization to an amphibious life history and associated evolutionary change in photosynthetic pathway in the C 4 grass tribe Orcuttieae, with the most ancestral condition retained in Neostapfia, the sister group to the other two vernal pool genera, Orcuttia and Tuctoria (Boykin et al 2010), and with loss of Kranz anatomy in submerged juvenile foliage of the more highly amphibious Orcuttia (Keeley 1998).…”

“…Growing appreciation for the importance of ecology in understanding evolutionary change and recent evidence indicating evolutionary decoupling of niche parameters warrants more attention to resolving the history of ecological factors in a phylogenetic context as well (e.g., Emery et al 2012, Töpel et al 2012, Arrigo et al 2013, Anacker & Strauss 2014, in part to characterize likely future responses of lineages to environmental change. Field-based descriptive and experimental work is invaluable to these goals and, although often difficult and unavoidably slow, continues to be the source of some of the most important contributions to evolutionary understanding of the California flora (e.g., Ramsey et al 2003, Angert & Schemske 2005, Lowry et al 2008.…”

Occupation of bare habitats, an evolutionary precursor to soil specialization in plants

“…[22][23][24][25]. Experiments with an explicit phylogenetic framework can address aspects of trait evolution, niche conservatism, adaptation, historical contingency, exaptations, phylogenetic lag, and genetic constraints (20,(26)(27)(28)(29)(30). Here, we expand on these approaches by also incorporating extensive ecological data collections taken across field sites occupied by members of a whole clade, and integrating them with common garden greenhouse experiments and phylogenetic hypotheses.…”

Revisão taxonômica, filogenia e evolução do nicho ecológico de Tynanthus Miers (Bignonieae, Bignoniaceae)

“…Fine-scale analyses of the distribution pattern of sympatric species would be of particular interest so that habitat use and fine-scale drivers of species distributions could be examined (see Emery et al 2012). Studies of this nature for Neotropical plant clades would be of particular interest given the high levels of diversity encountered in this region and the limited amount of ecological, evolutionary, and biogeographical studies.…”

“…It is now clear, that species ranges are determined by a set of abiotic and biotic conditions that are known as a species niche (Hutchinson 1957) which, together with historical factors, seem to have shaped present-day distribution patterns. In this context, it is critical that analyses of niche elements incorporate information on the phylogenetic history of the focal taxa so that a more complete picture of the factors shaping species distributions can be achieved (e.g., Rice et al 2003;Knouft et al 2006;Eaton et al 2008;Kozak & Wiens 2010;Emery et al 2012;Nyári & Reddy 2013). Niche studies based on robust phylogenetic frameworks allow us to identify how long-term evolutionary processes have led to present-day distribution patterns as well as to establish how species niches have changed and evolved over time (Wiens 2011).…”