Catchments catch all in South African coastal lowlands: multilocus phylogeography and distribution modelling of Nymania capensis (Meliaceae) reveal topographic and palaeoclimatic connectivity constraints

Alastair J Potts

doi:10.7287/peerj.preprints.2506v1

Catchments catch all in South African coastal lowlands: multilocus phylogeography and distribution modelling of Nymania capensis (Meliaceae) reveal topographic and palaeoclimatic connectivity constraints

Alastair J Potts

Centre for Coastal Palaeoscience, Nelson Mandela Metropolitan University, Port Elizabeth, Eastern Cape, South Africa

DOI: 10.7287/peerj.preprints.2506v1

Published: 2016-10-08
Accepted: 2016-10-08

Subject Areas: Biogeography, Conservation Biology, Molecular Biology, Plant Science
Keywords: Multilocus phylogeography, species palaeodistribution modelling, molecular dating, Nymania capensis, catchments; Last Glacial Maximum, Albany Subtropical Thicket, Orbitally-forced range dynamics

Copyright: © 2016 Potts
Licence: This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.

Cite this article: Potts AJ. 2016. Catchments catch all in South African coastal lowlands: multilocus phylogeography and distribution modelling of Nymania capensis (Meliaceae) reveal topographic and palaeoclimatic connectivity constraints. PeerJ Preprints 4:e2506v1 https://doi.org/10.7287/peerj.preprints.2506v1

Abstract

Background. This study investigates orbitally-forced range dynamics at a regional scale by exploring the evolutionary history of Nymania capensis (Meliaceae) across the deeply incised landscapes of the subescarpment coastal lowlands of South Africa; a region home to three biodiversity hotspots (Succulent Karoo, Fynbos, and Maputaland-Pondoland-Albany hotspots).

Methods. A range of methods are used including: multilocus phylogeography (chloroplast and high- and low-copy nuclear DNA), molecular dating and species distribution modelling (SDM).

Results. The results support an ‘evolutionarily distinct catchment’ hypothesis where: 1) diﬀerent catchments contain genetically distinct lineages, 2) limited genetic structuring was detected within basins whilst high structuring was detected between basins, and 3) within primary catchment populations display a high degree of genealogical lineage sorting. In addition, the results support a glacial refugia hypothesis as: a) the timing of chloroplast lineage diversiﬁcation is restricted to the Pleistocene in a landscape that has been relatively unchanged since the late Pliocene, and b) the projected LGM distribution of suitable climate for N. capensis suggest fragmentation into refugia that correspond to the current phylogeographic populations.

Discussion. This study highlights the interaction of topography and subtle Pleistocene climate variations as drivers affecting both seed and pollen flow along these lowlands. This lends support to the region’s large-scale conservation planning efforts, which used catchments as foundational units for conservation as these are likely to be evolutionary significant units.