About this Research Topic
This volume aims to address the complexity of tropical diversification processes from an empirical perspective with an emphasis on molecular phylogenetics and phylogeography but also with contributions from palaeontology and palaeoecology. It will emphasise the whole tropics, and especially Africa and South East Asia, which have been neglected in recent reviews. This global synthesis is necessary to achieve a reliable factual basis for more sound generalisations and theoretical proposals, as well as for testing already existing models and hypotheses. The topic has tremendous significance for the understanding of modern biodiversity and its conservation.
Since Darwin, one of the main questions in relation to the Earth’s biological diversity has been disentangling the causes for the comparatively high diversity in tropical zones, particularly the Neotropics. Prior to the development of studies incorporating DNA sequence data, the generally accepted hypothesis was based on palaeoecological evidence that considered that Quaternary glacial cycles fueled neotropical diversification through the alternation of glacial aridity and wet inter-glacials. This refuge hypothesis was later dismissed by the defendants of a competing hypothesis that suggested that most extant species were in fact of pre-Quaternary origin. This view emphasised that tectonically-driven palaeogeographic transformations caused the waxing and waning of biogeographic barriers, and opening and closing of migration routes.
The first DNA-based phylogenetic and phylogeographic studies were used to support this pre-Quaternary picture, but recent meta-analyses of dated neotropical DNA phylogenies indicated that speciation has proceeded in a continual fashion since the Miocene and through the Quaternary. Moreover, patterns and rates of diversification and biogeography have been shown to differ amongst different biomes and taxonomic groups. Therefore, the issue of the timing and environmental drivers of tropical diversification is not a black-and-white one; rather, the coupling of multiple factors acting synergistically at different spatial and temporal scales. This debate has primarily been argued in studies of Neotropical lineages but processes may have been different in other tropical regions. The scale of aridification in Africa was much grander than in the Neotropics or Southeast Asia. Diversification in Southeast Asia may have proceeded differently as a result of the mostly island nature of the region, its complex tectonic history and Quaternary sea-level changes. One of the goals of this issue is to augment the comparatively few studies in Africa, India and Australasia so that we may compare patterns and processes in different parts of the tropics.
To avoid potential biases, the following strategies are proposed:
• no constraints concerning paper types (original research, reviews, meta-analyses…) provided they fit within the journal rules
• papers can cover the whole tropical zone or be specific to particular regions, but we particularly welcome contributions addressing tropical Asia and Africa.
• studies of historical biodiversity trends will be considered, provided they have a direct influence on present-day diversity patterns
• any type of organisms, at any organisation level (intra-specific clades to entire communities) are acceptable
• studies on any kind of environmental driver, ecological process or genetic mechanism linked to the origin of tropical diversity can be addressed
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.