Patterns of diversification amongst tropical regions compared: a case study in Sapotaceae

Abstract

Species diversity is unequally distributed across the globe, with the greatest concentration occurring in the tropics. Even within the tropics, there are significant differences in the numbers of taxa found in each continental region. Manilkara is a pantropical genus of trees in the Sapotaceae comprising c. 78 species. Its distribution allows for biogeographic investigation and testing of whether rates of diversification differ amongst tropical regions. The age and geographical origin of Manilkara are inferred to determine whether Gondwanan break-up, boreotropical migration or long distance dispersal have shaped its current disjunct distribution. Diversification rates through time are also analyzed to determine whether the timing and tempo of speciation on each continent coincides with geoclimatic events. Bayesian analyses of nuclear (ITS) and plastid (rpl32-trnL, rps16-trnK, and trnS-trnFM) sequences were used to reconstruct a species level phylogeny of Manilkara and related genera in the tribe Mimusopeae. Analyses of the nuclear data using a fossil-calibrated relaxed molecular clock indicate that Manilkara evolved 32–29 million years ago (Mya) in Africa. Lineages within the genus dispersed to the Neotropics 26–18 Mya and to Asia 28–15 Mya. Higher speciation rates are found in the Neotropical Manilkara clade than in either African or Asian clades. Dating of regional diversification correlates with known palaeoclimatic events. In South America, the divergence between Atlantic coastal forest and Amazonian clades coincides with the formation of drier Cerrado and Caatinga habitats between them. In Africa diversification coincides with Tertiary cycles of aridification and uplift of the east African plateaux. In Southeast Asia dispersal may have been limited by the relatively recent emergence of land in New Guinea and islands further east c. 10 Mya.

Using dated molecular phylogenies to help reconstruct geological, climatic, and biological history: Examples from Colombia

“…Dated molecular phylogenies have supported that the most likely outcome has been migration away from increasingly unsuitable areas that is consistent with their lack of adaptability, for example, Couvreur, Chatrou, Sosef, and Richardson (2008); Armstrong et al (2015). Dated molecular phylogenies have supported that the most likely outcome has been migration away from increasingly unsuitable areas that is consistent with their lack of adaptability, for example, Couvreur, Chatrou, Sosef, and Richardson (2008); Armstrong et al (2015).…”

“…The uplift of mountain ranges can also cause significant rain shadow effects (e.g., Houston & Hartley, 2003) Brazil (Armstrong et al, 2015) more or less coincided with diversification of cerrado restricted lineages (Simon et al, 2009)…”

“…The uplift of mountain ranges can also cause significant rain shadow effects (e.g., Houston & Hartley, 2003) (Armstrong et al, 2015) more or less coincided with diversification of cerrado restricted lineages (Simon et al, 2009). Splits in an African wet forest restricted lineage in Annonaceae were shown to coincide with suspected periods of aridification on the continent that were caused by geological events and that would have led to a contraction in wet forests (Couvreur et al, 2008).…”

“…2 | PHYLOGENETIC NICHE CONSERVATISM -HOW WE CAN USE IT TO UNDERSTAND GEOLOGY AND PALAEOCLIMATE Faced with climatic changes, living organisms may react in three different ways: either they remain at the same location and adapt or if they do not have the capacity to adapt, they migrate to climatically suitable localities or they go extinct. Dated molecular phylogenies have supported that the most likely outcome has been migration away from increasingly unsuitable areas that is consistent with their lack of adaptability, for example, Couvreur, Chatrou, Sosef, and Richardson (2008); Armstrong et al (2015). Using biotic history to trace geological and climatic history is dependent on phylogenetic niche conservatism (PNC), which is the tendency of species to retain their ancestral traits (Wiens & Graham, 2005).…”

Freezing and water availability structure the evolutionary diversity of trees across the Americas

“…1). The 52 extratropical group is not geographically segregated, but includes temperate tree 53 assemblages from North America and southern South America, connected by a 54 Figure 1 The geographic, evolutionary and environmental relationships of the two principal 56 evolutionary groups (from K=2 clustering analysis). A) Geographic distribution of angiosperm tree 57 assemblages and their affiliation with either the tropical (n = 7145) or extratropical (n = 2792) evolutionary 58 group; B) Distribution of assemblages over elevation and latitude showing that the extratropical group is 59 largely restricted to high elevations at low latitudes; C & D) Distribution of assemblages over the first two 60 axes of an ordination based on evolutionary composition with assemblages in C colored according to group 61 affiliation and in D as to whether or not they experience freezing temperatures in a regular year (from (31 )).…”