Environmental Niche Divergence In The Kalmia Lineage: Integrating Phylogeny, Community Composition And Ecology To Understand Patterns Of Regional Plant Diversity

The ongoing synthesis of the formerly disparate fields of ecology and evolution is resulting in a proliferation of insights, highlighting the interdependence and feedback between ecological and evolutionary processes. There is increasing evidence that evolutionary processes can influence community dynamics through geographic patterns of speciation, mutualist interactions, and other processes governing community phylogenetic patterns (Weber et al., 2017; Weeks et al., 2016). Here we adopt a clade-focused perspective to understand patterns of niche evolution in a single lineage, and subsequently address the regional community context of habitats which have facilitated the persistence and diversification of members of the genus. Hypothesized to have originated in eastern North America, the genus Kalmia contains ten species exhibiting widely varying and disjunct distributions while occupying a large spectrum of habitats- from alpine bogs to xeric sandhill scrub (Gillespie & Kron, 2013; Weakley, 2015). Given the extent of ecological and geographic divergence, we asked the following questions: what potential processes or factors underlie the patterns of lineage bifurcation and habitat differentiation in Kalmia, and what has been the role of phylogenetic niche conservatism in these lineage divergences? We constructed ecological niche models for seven of ten species of Kalmia using available climatic and topographic variables, and identified the variables contributing most to the observed distributions. We calculated niche overlap among all species, and subsequently used these metrics to assess the potential geographic pattern of divergence using a recent molecular phylogeny for the genus. We then subjected these results to an age-range correlation (ARC) test. We assessed the extent of niche conservatism in both morphological as well as abiotic traits that we could further use to infer processes underlying niche evolution. We suggest that the long evolutionary history of the Kalmia lineage in eastern North America coinciding with climatic and/or topographic changes has resulted in considerable niche lability, subsequently allowing Kalmia species to track suitable oligotrophic habitats while diverging in larger-scale climatic and topographic niche characteristics as well as less ecologically important morphological traits.To understand speciation and niche evolution in a community context, we investigated the habitat use among three of these closely related taxa that exhibit overlapping disjunct ranges. We assessed the taxonomic and phylogenetic patterns of local communities along an elevation gradient among three distinct floristic regions of the southeastern US that all contain at least one Kalmia species. We asked if there were differences in abiotic and biotic attributes among coastal plain, piedmont and mountain habitats, given that they all support the same focal taxa. Using community data from both field collection and an open-source vegetation database, we find that differences in edaphic and phylogenetic patterns among regions were minimal with only soil pH exhibiting differences. Our results of taxonomic and phylogenetic beta diversity support the prevalence of allopatric speciation patterns from closely related lineages establishing in similar habitats. This research highlights the importance of considering habitat-specific lineage pools when interpreting patterns of regional diversity and local community assembly, as well as consideration for lineage-specific history when evaluating regional diversity patterns

Microsatellite markers for the biogeographically enigmatic sandmyrtle (Kalmia buxifolia, Phyllodoceae: Ericaceae)

Premise: Microsatellite markers were developed for sandmyrtle, Kalmia buxifolia (Ericaceae), to facilitate phylogeographic studies in this taxon and possibly many of its close relatives. Methods and Results: Forty‐eight primer pairs designed from paired‐end Illumina MiSeq data were screened for robust amplification. Sixteen pairs were amplified again, but with fluorescently labeled primers to facilitate genotyping. Resulting chromatograms were evaluated for variability using three populations from Tennessee, North Carolina, and New Jersey, USA. Eleven primer pairs were reliable and polymorphic (mean 3.92 alleles), one was reliable but monomorphic, and four were not reliable. The markers exhibited lower heterozygosity (mean 0.246) than expected (mean 0.464). Cross‐amplification in the remaining nine Kalmia species exhibited a phylogenetic pattern, suggesting broad applicability of the markers across the genus. Conclusions: These microsatellite markers will be useful in population genetics and species boundaries studies of K. buxifolia, K. procumbens, and likely all other Kalmia species.publishedVersio

Microsatellite markers for the biogeographically enigmatic sandmyrtle (Kalmia buxifolia, Phyllodoceae: Ericaceae)

Premise: Microsatellite markers were developed for sandmyrtle, Kalmia buxifolia (Ericaceae), to facilitate phylogeographic studies in this taxon and possibly many of its close relatives. Methods and Results: Forty‐eight primer pairs designed from paired‐end Illumina MiSeq data were screened for robust amplification. Sixteen pairs were amplified again, but with fluorescently labeled primers to facilitate genotyping. Resulting chromatograms were evaluated for variability using three populations from Tennessee, North Carolina, and New Jersey, USA. Eleven primer pairs were reliable and polymorphic (mean 3.92 alleles), one was reliable but monomorphic, and four were not reliable. The markers exhibited lower heterozygosity (mean 0.246) than expected (mean 0.464). Cross‐amplification in the remaining nine Kalmia species exhibited a phylogenetic pattern, suggesting broad applicability of the markers across the genus. Conclusions: These microsatellite markers will be useful in population genetics and species boundaries studies of K. buxifolia, K. procumbens, and likely all other Kalmia species.publishedVersio

Microsatellite markers for the biogeographically enigmatic sandmyrtle (Kalmia buxifolia, Phyllodoceae: Ericaceae)

Premise: Microsatellite markers were developed for sandmyrtle, Kalmia buxifolia (Ericaceae), to facilitate phylogeographic studies in this taxon and possibly many of its close relatives. Methods and Results: Forty‐eight primer pairs designed from paired‐end Illumina MiSeq data were screened for robust amplification. Sixteen pairs were amplified again, but with fluorescently labeled primers to facilitate genotyping. Resulting chromatograms were evaluated for variability using three populations from Tennessee, North Carolina, and New Jersey, USA. Eleven primer pairs were reliable and polymorphic (mean 3.92 alleles), one was reliable but monomorphic, and four were not reliable. The markers exhibited lower heterozygosity (mean 0.246) than expected (mean 0.464). Cross‐amplification in the remaining nine Kalmia species exhibited a phylogenetic pattern, suggesting broad applicability of the markers across the genus. Conclusions: These microsatellite markers will be useful in population genetics and species boundaries studies of K. buxifolia, K. procumbens, and likely all other Kalmia species

Altered precipitation has asymmetric impacts on annual plant communities in warm and cool growing seasons

While altered precipitation regimes can greatly impact biodiversity and ecosystem functioning, we lack a comprehensive view of how these impacts are mediated by changes to the seasonality of precipitation (i.e., whether it rains more/less in one season relative to another). Over 2 years, we examined how altered seasonal precipitation influenced annual plant biomass and species richness, Simpson’s diversity, and community composition of annual plant communities in a dryland ecosystem that receives both winter and summer rainfall and has distinct annual plant communities in each season. Using a rainfall exclusion, collection, and distribution system, we excluded precipitation and added water during each season individually and compared responses to control plots which received ambient summer and winter precipitation. In control plots, we found five times greater annual plant biomass, twice as many species, and higher diversity in winter relative to summer. Adding water increased annual plant biomass in summer only, did not change richness or diversity in either summer or winter, and modestly shifted community composition. Excluding precipitation in either season reduced annual plant biomass, richness, and Simpson’s diversity. However, in the second winter season, biomass was higher in the plots where precipitation was excluded in the previous summer seasons suggesting that reduced productivity in the summer may facilitate biomass in the winter. Our results suggest that increased precipitation in summer may have stronger short-term impacts on annual plant biodiversity and ecosystem function relative to increased winter precipitation. In contrast, decreasing precipitation may have ubiquitous negative effects on annual plants across both summer and winter but may lead to increased biomass in the following off-seasons. These patterns suggest that annual plant communities exhibit asymmetries in their community and ecosystem responses to altered seasonal precipitation and that considering the seasonality of precipitation is important for predicting the effects of altered precipitation regimes

Predicting intraspecific trait variation among California's grasses

Plant species can show considerable morphological and functional variation along environmental gradients. This intraspecific trait variation (ITV) can have important consequences for community assembly, biotic interactions, ecosystem functions and responses to global change. However, directly measuring ITV across many species and wide geographic areas is often infeasible. Thus, a method to predict spatial variation in a species’ functional traits could be valuable. We measured specific leaf area (SLA), height and leaf area (LA) of grasses across California, covering 59 species at 230 sampling locations. We asked how these traits change along climate gradients within each species and used machine learning to predict local trait values for any species at any location based on phylogenetic position, local climate and that species’ mean traits. We then examined how much these local predictions alter patterns of assemblage-level trait variation across the state. Most species exhibited higher SLA and grew taller at higher temperatures and produced larger leaves in drier conditions. The random forests predicted spatial variation in functional traits very accurately, with correlations up to 0.97. Because trait records were spatially biased towards warmer areas, and these areas tend to have higher SLA individuals within each species, species means of SLA were upwardly biased. As a result, using species means over-estimates SLA in the cooler regions of the state. Our results also suggest that height may be substantially under-predicted in the warmest areas. Synthesis. Using only species mean traits to characterize the functional composition of communities risks introducing substantial error into trait-based estimates of ecosystem properties including decomposition rates or NPP. The high performance of random forests in predicting local trait values provides a way forward for estimating high-resolution patterns of ITV without a massive data collection effort