J. Levinton et al., MOLECULAR-DATA AND BIOGEOGRAPHY - RESOLUTION OF A CONTROVERSY OVER EVOLUTIONARY HISTORY OF A PAN-TROPICAL GROUP OF INVERTEBRATES, Journal of experimental marine biology and ecology, 203(1), 1996, pp. 117-131
Phylogenetic analyses of sequences of 16S rDNA suggest that the curren
t hypothesis of the evolution of the pan-tropical fiddler crab genus U
ca (Decapoda, Brachyura, Ocypodidae) is false. This hypothesis rests o
f the assumption that the increase of complexity of reproductive behav
ior, together with a tendency of a habitat shift towards the higher in
tertidal, arose only once in the history of the fiddler crabs. The ori
gin of fiddler crabs was placed in the IndoPacific, which is widely th
ought to be a center of origin for several marine groups. There, relat
ively lower intertidal crabs were thought to give rise to a radiation
in the Americas in which higher intertidal forms with more complex rep
roductive behavior evolved, and finally, derived crabs were thought to
disperse back to the IndoPacific from the Americas, In contrast our p
hylogeny suggests that the ancestral group, which shows complex reprod
uctive behavior, now resides wholly in the American-Atlantic region, a
s opposed to the postulated Indo-west-Pacific. Behavioral and ecologic
al complexity must have arisen independently in the American and IndoP
acific faunal regions. The pan-tropical subgenus Celuca seems to be po
lyphyletic, which suggests that the evolution of morphology, ecology a
nd behavior involves convergence in geographically separated locales.
This study highlights the dangers of postulating evolution from a cent
er of origin, even if it fits data that can be assigned to an evolutio
nary trend.