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DIVERGENCE BETWEEN POPULATIONS OF A MONOGAMOUS POLYCHAETE WITH MALE PARENTAL CARE: PREMATING ISOLATION AND CHROMOSOME VARIATION
Citation:
Weinberg, J., V. Starczak, C. Mueller, G. Pesch, AND S. Lindsay. DIVERGENCE BETWEEN POPULATIONS OF A MONOGAMOUS POLYCHAETE WITH MALE PARENTAL CARE: PREMATING ISOLATION AND CHROMOSOME VARIATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-90/518 (NTIS PB91206904).
Description:
Low dispersal and sexual selection are characteristic of the coastal polychaete Nereis acuminata Ehlers 1868 [also known as Nereis arenaceodentata Moore 1903 and Nereis (Neanthes) caudata elle Chiaje 1841]. e assessed levels of premating isolation between populations of this polychaete. our North American populations were used, two from the Atlantic and two from the Pacific. orms from all sites (1) were collected in 1987 and 1988 from the same habitat type, (2) were morphologically similar and keyed out as N. acuminata, and (3) reproduced monogamously and exhibited male parental care, an extremely rare reproductive mode in marine invertebrates. here was no evidence from 10-minor 36-h trials of premating isolation between the two Pacific populations. Incomplete premating isolation was found between the two Atlantic populations. igh aggression and non-pairing occurred in some 10-min trials between males and females. owever, in 36-h trials males and females from the two Atlantic populations always paired to mate. omplete premating isolation was found between Atlantic and Pacific populations. uring 10-min trials, males and females from different oceans often attacked and then avoided each other, and they never paired to mate. or did they pair to mate in longer, 36-h trials. ne Pacific and one Atlantic population were compared for tolerance to cold temperature. acific individuals were less able to tolerate cold water than Atlantic individuals. Two Atlantic populations studied had karyotypes with 11 pairs of small acrocentric chromosomes (2n = 22), while the two Pacific populations had nine pairs of large metacentric or submetacentric chromosomes (2n = 18). uch extreme dissimilarity in karyotype was not expected considering the similarity in morphology, habitat, and reproductive mode. esults suggest strongly that the Atlantic and Pacific populations have been allopatric for a long time, and are different species.
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DIVERGENCE BETWEEN POPULATIONS OF A MONOGAMOUS POLYCHAETE WITH MALE PARENTAL CARE: PREMATING ISOLATION AND CHROMOSOME VARIATION