The hypothesis of sympatric speciation as the dominant generator of endemism in a global hotspot of biodiversity

Abstract

Allopatric or sympatric speciation influence the degree to which closely related species coexist in different manners, altering the patterns of phylogenetic structure and turnover among and between communities. The objective of this study was to examine whether phylogenetic community structure and turnover in the Brazilian Atlantic Forest permit conclusions about the dominant process for the formation of extant angiosperm richness of tree species. Therefore, we analyzed phylogenetic community structure (MPD, MNTD) as well as taxonomic (Jaccard similarity) and phylogenetic turnover (betaMPD, betaMNTD) among and between 49 tree communities distributed among three different habitat types. Mean annual precipitation and mean annual temperature in each survey area were estimated. Phylogenetic community structure does not differ between habitat types, although MPD reduces with mean annual temperature. Jaccard similarity decreases and betaMNTD increases with spatial distance and environmental differences between study sites. Spatial distance explains the largest portions of variance in the data, indicating dispersal limitation and the spatial aggregation of recently formed taxa, as betaMNTD is related to more recent evolutionary events. betaMPD, that is related to deep evolutionary splits, shows no spatial or environmental pattern, indicating that older clades are equally distributed across the Brazilian Atlantic Forest. While similarity pattern indicates dispersal limitations, the spatial turnover of betaMNTD is consistent with a high degree of sympatric speciation generating extant diversity and endemism in the Brazilian Atlantic Forest. More comprehensive approaches are necessary to reduce spatial sampling bias, uncertainties regarding angiosperm diversification patterns and confirm sympatric speciation as the dominant generator for the formation of extant species diversity in the Brazilian Atlantic Forest.

Structures of tropical dry forests in the Andes: forest conservation, composition and the role of fabaceae and myrtaceae

“…Floristic and phytosociological surveys in the Neotropics have generated, over more than 40 years, an extensive database that today allows us to understand how landscape, climate, altitude, soils and history affect phytogeography, diversity, evolution and ecology, from populations and communities to entire biomes (e.g., Bueno et al, 2016;Gastauer et al, 2015;Lima et al, 2020;Neves et al, 2020;Fontes, 2000). Tropical Dry Forests (TDFs) have less than 1000 mm of rainfall in tropical and equatorial latitudes (see Oliveira-Filho et al 2015) and are less studied by floristic and phytosociological studies than other large biomes with woody vegetation (Andrade et al, 2011), but the absence of this type of study is especially worrying with the climate change predicted for the coming decades (IPCC, 2021) in mountains such as the Andes where isolated fragments of TDFs will have their climates altered in heavily anthropized landscapes (Galván-Cisneros et al, 2021).…”

Rules of Plant Species Ranges: Applications for Conservation Strategies

“…Recent research has supported the case that plant species generally begin small, "budding" from parental species, often sympatrically within the parent species range, and then expanding over time through niche evolution and/or dispersing more widely over time (Grossenbacher et al, 2014;Anacker and Strauss, 2014). Recent literature mainly sustains this view (Gastauer et al, 2015;Heydel et al, 2017;Skeels and Cardillo, 2018), but there is important variation, nuance, and exception, and a variety of forms of speciation and specialization in plants (Boucher et al, 2016;Rajakaruna, 2018;Salariato and Zuloaga, 2021). For example, a species may evolve through adaptation to a niche that is very widespread (e.g., ruderal plants), and so it has the potential to fill this niche quickly and will appear, geologically, as if it expanded its niche rapidly and exploded.…”

Updated angiosperm family tree for analyzing phylogenetic diversity and community structure

“…The phylogenetic structure of a biological community determines whether species that coexist within a given community are more closely related than expected by chance, and is essential information for investigating community assembly rules (Kembel & Hubbell 2006;Gastauer & Meira-Neto 2014a;Miazaki et al 2015;Lamare et al 2016) as well as determining the evolutionary processes that generated extant biodiversity (Fine & Kembel 2011;Gastauer et al 2015a). More recently, the use of phylogenetic diversity to describe the amount of evolutionary history represented within a sample has gained importance as an indicator for conservation purposes (Forest et al 2007;Huang et al 2016;Arponen & Zupan 2016).…”