Ngoma, E., S. Valdesalici, K. Reichwald & A. Cellerino. 2013. Genetic
and morphological Studies of Nothobranchius
(Cyprinodontiformes) from Malawi with Description of
Nothobranchius wattersi sp. nov. J. Fish Biol., 82 (1): 178, Figs. 5c,
5d, 5e, 5f.
Abstract
Molecular and morphological data were used to explore
evolutionary differentiation among populations of Nothobranchius
in the Lake Malawi-upper Shire River and the Lakes Chilwa-Chiuta
drainage systems in Malawi. The aim of the study was to test the
hypothesis that Nothobranchius of the Malawi-Shire system
constitute a separate evolutionary group from Nothobranchius
kirki. Mitochondrial and nuclear sequence data show a strongly
supported phylogenetic split into two monophyletic groups
separating the Lake Malawi basin fish from N. kirki. Unlike N. kirki,
Lake Malawi-Shire fish do not deviate from neutrality and express
an excess of rare haplotypes and mutations in terminal branches,
characteristic of recently expanded populations. Further, the two
groups significantly differ in morphology. Two body characters
(dorsal-fin base length and pre-pelvic-pre-anal distance) are
significantly different between the two species in both sexes.
Several other characters are significantly different in either male
or female comparisons with respect to both standard and head
lengths, and robust morphological differentiation is detected by
multivariate analysis. The two groups are readily distinguished on
the basis of male colouration, especially in scale centres and the
caudal fin. On the basis of this differentiation at the molecular and
morphological levels, in addition to colouration, the Lake Malawi-
Shire fish are hereby formally recognized as constituting a new
species, Nothobranchius wattersi. This distinction is in agreement
with the geomorphologic and recent climatic history in the region.
© 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries
Society of the British Isles.