C. Fragoso et P. Rojas, SIZE SHIFT IN THE MEXICAN EARTHWORM SPECIES BALANTEODRILUS-PEARSEI (MEGASCOLECIDAE, ACANTHODRILINI) - A POSSIBLE CASE OF CHARACTER DISPLACEMENT, Soil biology & biochemistry, 29(3-4), 1997, pp. 237-240
The earthworm genus Balanteodrilus includes three well-differentiated
species. One of the species (B. pearsei) is common to eastern and sout
h-eastern Mexico. All but one population of B. pearsei are medium-size
d earthworms (6.4-11 cm in length). The smallest morph of B. pearsei w
as found sympatrically coexisting at La Mancha forest with another spe
cies of the genus. In this locality, resources are scarce, the two spe
cies present different vertical distributions and their abundances are
relatively low. A change of size in this population was not the resul
t of random variation. Three possible explanations are proposed: (1) c
haracter displacement resulting from past long-term competition; (2) r
esponse to poor soil nutrients; or (3) reproductive character displace
ment or reinforcement. (C) 1997 Elsevier Science Ltd.