Sexual dimorphism and population divergence in Tropheus

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Bojan Dolenc
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Sexual dimorphism and population divergence in Tropheus

Post by Bojan Dolenc » Sat Jan 23, 2010 7:08 am

Herler J, Kerschbaumer M, Mitteroecker P, Postl L, Sturmbauer C. 2010. Sexual dimorphism and population divergence in the Lake Tanganyika cichlid fish genus Tropheus. Frontiers in Zoology 7: 4 doi: 10.1186/1742-9994-7-4

Background
With about 120 colour morphs currently assigned to six nominal species, the genus Tropheus is an ideal model to study evolutionary divergence of populations in allopatry. The morphology of Tropheus has been described as relatively static, but reproductive constraints are sexually dimorphic due to mouthbrooding in females. We analysed phenotypic variation in six populations of T. moorii and one population of T. polli using geometric morphometrics to assess morphological differences among sexes in relation to the differentiation of populations and species.

Results
The mean shapes differed significantly between sexes, populations, and species even though within-sex variation exceeded the divergence among populations. The first principal component of Procrustes shape coordinates revealed differences between populations and species in mouth position and ventral head shape. The second principal component reflected sex-specific shape differences, mainly comprising a relatively larger female viscerocranium and, in particular, a larger buccal area. While shape variation between populations and between sexes was primarily located in the cranial region, within-sex variation was relatively uniform across all landmarks.

Conclusions
Deviations of the between-population and between-sex pattern of shape variation from that within sex indicate that the differences in head shape likely result from both adaptations to female mouthbrooding and population-specific foraging strategies.
Change in habit, producing change of function, is the main cause of the production of change in living structure. F. Wood Jones (1953) Trends of life

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Pam Chin
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Re: Sexual dimorphism and population divergence in Tropheus

Post by Pam Chin » Sat Jan 23, 2010 2:17 pm

Interesting, thank you!

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