An Experimental Evaluation of Premating Isolation in the Hyla ewingi Complex (Anura: Hylidae)

Abstract

would not be effective as an isolating mechanism. Secondly, since the range of variation of pulse repetition rate in deep sympatric H. verreauxidid not overlap that of allopatric H. verreauxi (a difference comparable with that seen in the heterospecific sympatric populations), premating reproductive isolation of these populations was predicted.Although differences in mating calls have been shown to operate as important premating isolating mechanisms in other species of hylid frogs (Blair and Little john, 1960;Littlejohn, 1960Littlejohn, , 1961Littlejohn, Fouquette, and Johnson, 1960;Littlejohn and Michaud, 1959;Michaud, 1962;Snyder and Jameson, 1965), direct experimental evidence was lacking in the H. ewingi complex. Accordingly, a program of call discrimination trials was arranged in order to test the assumption that the mating call differences were operating as premating isolating mechanisms. Since the calls of shallow sympatric H. ewingi are similar to those of adjacent allopatric H. ewingi, the predictions about the degree of premating isolation present between the two allopatric populations could also be tested. For practical reasons it was possible to test female H. ewingi and H. uerreauxi from only one area-western sympatry. Even so, the results of the trials are convincing, allowing some conclusions and further predictions to be made.

REPRODUCTIVE CHARACTER DISPLACEMENT IN CALOPTERYX (ODONATA: CALOPTERYGIDAE)

“…Littlejohn, 1965;Littlejohn and Loftus-Hills, 1968;Grant, 1975;Waage, 1975 and present study). It allows an assessment of the functional significance of the characters involved, the discrimination ability of the species involved, and the degree of divergence necessary to effect isolation.…”

“…These stages were stated or implied by Grant (1972Grant ( , 1975 and others (e.g. Alexander, 1969;Littlejohn, 1965;Littlejohn and Loftus-Hills, 1968) and are summarized as follows:…”

Hybridization in Plants: Old Ideas, New Techniques

“…During the modern synthesis, Dobzhansky (1940) first clearly articulated how greater assortative mating could be favored by selection to decrease hybridization and maintain coadapted gene complexes. Although much of the formative research on reinforcement was done in animal systems (Dobzhansky and Koller, 1938;Blair, 1955;Dobzhansky et al, 1964;Littlejohn and Loftus-Hills, 1968), there is a long history of botanical research on reinforcement as well (Grant, 1966;Levin and Kerster, 1967;McNeilly and Antonovics, 1968;Paterniani, 1969;Whalen, 1978).…”

Mate Discrimination and Cuticular Hydrocarbons in Drosophila elegans and D. gunungcola

“…In fact, it has been observed that calling sounds of Hyla (Littlejohn and Luftus-Hills, 1968) and wing coloration of Calopteryx (Waage, 1979) differ more where they occur sympatrically than where they occur allopatrically. The present study species, D. elegans and D. gunungcola are reported to occur sympatrically at least at high altitudes in Indonesia (Sultana et al, 1999;Suwito et al, in press).…”

“…For example, a pair of species often differ more with each other where they are sympatric than where they are allopatric (Brown and Wilson, 1956). This phenomenon, called character displacement, is assumed to reflect the evolution to reduce interspecific competition (Grant, 1972(Grant, , 1975 or prevent interspecific mating (Ehrman, 1965;Littlejohn, 1965;Littlejohn and Luftus-Hills, 1968;Dobzhansky et al ., 1969;Wasserman and Koepfer, 1977;Waage, 1979;Orr, 1989, 1997). In this paper, we examine whether or not the evolution of mate recognition system of Drosophila elegans Bock and Wheeler has been affected by the presence of its sibling D .…”