Where did all the trees come from? A novel multispecies approach reveals the impacts of biogeographical history and functional diversity on rain forest assembly

Abstract

Aim We take advantage of next generation sequencing-based technology to assess how landscape-level dynamics, biogeographical history and functional factors shape the distribution of genetic diversity in rain forest trees. To achieve this, we explore chloroplast genomic diversity and divergence patterns across multiple, co-distributed species from three major centres of rain forest diversity.Location Subtropical rain forests in south-eastern Australia: Nightcap-Border Ranges, Dorrigo and Washpool.Methods We assembled chloroplast genomic data from whole-genome shotgun libraries for 71 species collected across three major centres of rain forest diversity. Chloroplast single nucleotide polymorphisms were used to measure genetic variation within and between multiple populations, species and locations, and we used this information to identify patterns related to landscapelevel processes, biogeographical origins and functional characteristics.Results We identified Nightcap-Border Ranges and Dorrigo as containing multiple refugia and Washpool as primarily a recolonized area. We found that rapidly expanding lineages of Indo-Malesian origin exhibit significantly lower levels of genetic diversity than Gondwanan lineages with longer local histories. Functional traits related to persistence and dispersal were the most important in regulating the distribution of genetic diversity. Main conclusionsThe distribution and assembly of species reflect interactions and competition between different floristic elements at different stages of continental occupation. Additionally, given the multiple evolutionary origins and histories of the Australian rain forest flora, it is important to avoid treating rain forest communities as single management units.

Filters of floristic exchange: How traits and climate shape the rain forest invasion of Sahul from Sunda

“…In our study, we show that important refugial areas in AWT and NNSW (Nightcap‐Border Ranges and Dorrigo) may have resisted Sunda invasion. We observed the expected lower proportions of Sunda lineages in NNSW including the Nightcap‐Border Ranges and Dorrigo regions (compared to AWT), and note a similar pattern in Washpool, a primarily recolonized area (Kooyman et al., ; Rossetto, McPherson, et al., ). This suggests that while Sahul lineages were able to recolonize Washpool from neighbouring refugia (within Nightcap‐Border Ranges and Dorrigo), the number of Sunda lineages able to colonize from source populations (assumed to be further north) was limited.…”

“…A significant per‐plot reduction of Sunda species proportion and richness ( p < .001 using Tukey HSD post hoc test, Figure ; Table ) was also observed between Nightcap‐Border Ranges (north) and Dorrigo (to the south). These two areas are separated by the Clarence River Corridor, a previously recognized biogeographical barrier (Rossetto, McPherson, et al., ).…”

“…For a comparative analysis of functional traits, we investigated if there were any characteristics common to Australian woody species with Sunda ancestry, and any differences between species with Sunda versus Sahul ancestry. We used continuous trait‐measures for leaf size (surface area), fruit size, wood density and maximum height at maturity, as well as categorical data from dispersal (mode) and persistence (resprouting) traits, all previously used in Australian rain forest studies (Kooyman et al., , , ; Rossetto & Kooyman, ; Rossetto et al., ; Rossetto, McPherson, et al., ; Rossetto, Kooyman, et al., ). Both the continuous and categorical traits were taken from published floras and other sources for all species (references listed in Appendix S2).…”

Evolutionary constraints and adaptation shape the size and colour of rain forest fruits and flowers at continental scale

“…The result of those habitat contractions was the retreat of rain forest to refugia in the wettest places. Depending on the topography and proximity to the coast, the rain forest refugia varied in size and distribution through time, with both the distance between remnant patches and the effective population sizes of local species changing with them (Kooyman et al, ; Mellick et al, ; Rossetto, McPherson, et al, ). For plants, these processes impacted on the fitness and viability of populations, the between‐refugia dynamics and the potential for expansion and recolonization (Rossetto, Crayn, Ford, Ridgeway, & Rymer, ; Rossetto et al, ; ).…”

The Phylogeny and Biogeography of Phyla nodiflora (Verbenaceae) Reveals Native and Invasive Lineages throughout the World

“…This is not an unusual finding (but see [64]). For example, in a whole chloroplast genome study of 71 rainforest taxa, Rossetto et al [65] found 75% of the trees sequenced (up to 18 individuals per species) had less than 25 single nucleotide polymorphisms across an average of 122,373 bp sequenced. Diazgranados & Barber [66], working with 110 species in the subtribe Espeletiinae Cuatrec., Asteraceae, found that most chloroplast regions screened were uninformative or the variability was too low to resolve phylogenetic relationships.…”