TY - JOUR
T1 - The impact of seasonality on niche breadth, distribution range and species richness
T2 - A theoretical exploration of Janzen’s hypothesis
AU - Hua, Xia
N1 - Publisher Copyright:
© 2016 The Author(s) Published by the Royal Society. All rights reserved.
PY - 2016/7/27
Y1 - 2016/7/27
N2 - Being invoked as one of the candidate mechanisms for the latitudinal patterns in biodiversity, Janzen’s hypothesis states that the limited seasonal temperature variation in the tropics generates greater temperature stratification across elevations, which makes tropical species adapted to narrower ranges of temperatures and have lower effective dispersal across elevations than species in temperate regions. Numerous empirical studies have documented latitudinal patterns in species elevational ranges and thermal niche breadths that are consistent with the hypothesis, but the theoretical underpinnings remain unclear. This study presents the first mathematical model to examine the evolutionary processes that could back up Janzen’s hypothesis and assess the effectiveness of limited seasonal temperature variation to promote speciation along elevation in the tropics. Results suggest that trade-offs in thermal tolerances provide a mechanism for Janzen’s hypothesis. Limited seasonal temperature variation promotes gradient speciation not due to the reduction in gene flow that is associated with narrow thermal niche, but due to the pleiotropic effects of more stable divergent selection of thermal tolerance on the evolution of reproductive incompatibility. The proposed modelling approach also provides a potential way to test a speciation model against genetic data.
AB - Being invoked as one of the candidate mechanisms for the latitudinal patterns in biodiversity, Janzen’s hypothesis states that the limited seasonal temperature variation in the tropics generates greater temperature stratification across elevations, which makes tropical species adapted to narrower ranges of temperatures and have lower effective dispersal across elevations than species in temperate regions. Numerous empirical studies have documented latitudinal patterns in species elevational ranges and thermal niche breadths that are consistent with the hypothesis, but the theoretical underpinnings remain unclear. This study presents the first mathematical model to examine the evolutionary processes that could back up Janzen’s hypothesis and assess the effectiveness of limited seasonal temperature variation to promote speciation along elevation in the tropics. Results suggest that trade-offs in thermal tolerances provide a mechanism for Janzen’s hypothesis. Limited seasonal temperature variation promotes gradient speciation not due to the reduction in gene flow that is associated with narrow thermal niche, but due to the pleiotropic effects of more stable divergent selection of thermal tolerance on the evolution of reproductive incompatibility. The proposed modelling approach also provides a potential way to test a speciation model against genetic data.
KW - Gradient speciation
KW - Janzen’s hypothesis
KW - Latitudinal diversity gradient
KW - Niche evolution
KW - Temperature tolerance
UR - http://www.scopus.com/inward/record.url?scp=84979673476&partnerID=8YFLogxK
U2 - 10.1098/rspb.2016.0349
DO - 10.1098/rspb.2016.0349
M3 - Article
SN - 0962-8452
VL - 283
JO - Proceedings of the Royal Society B: Biological Sciences
JF - Proceedings of the Royal Society B: Biological Sciences
IS - 1835
M1 - 20160349
ER -