Title

Cytogenetic study of the lower Central American frogs of the subgenus Craugastor (Anura: Leptodactylidae: Eleutherodactylus)

Date of Award

2001

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biology

First Committee Member

Jay M. Savage, Committee Chair

Abstract

Thirty-two karyomorphs belonging to 29 species of Eleutherotherodactylus from lower Central America and Puerto Rico were karyologically studied using C-banding and silver staining. Karyotypes of 16 species were described for the first time. Males of E. vocator have a heteromrophic pair #7 that could be sexually dimorphic, with an XX-XY sex determining mechanism. Two supernumerary chromosomes (B chromosomes) of Eleutherodactylus sp. B (20) derived from pair #9 by aneuploidy were hypothesized and reported for the first time in the family Leptodactylidae. The chromosomes of two uncertain species, E. sp. D (reported as E. diastema) and E. bransfordii, are confirmed as 2N = 18 and NF = 36.The chromosome data and banding karyotypes are informative and species specific. The major changes in chromosome number in the subgenus Craugastor are derived by Robertsonian fission or fusion and the NF value changes are mainly from pericentromeric inversion and addition of heterochromatin in the short arm of the telocentric chromosomes. Heterochromatin also plays a major role in the repatterning of chromosomes.All karyotypes have distinctive centromeric C-bands. The double interstitial C-bands are phylogenetic markers in E. gollmeri and the rhodopis groups.The NOR-carrying chromosomes are phylogenetic markers, especially among species of the rhodopis and biporcatus group. Some extra-NORs found in E. melanostictus, E. fitzingeri, and E. obesus are not phylogenetically informative.A model karyotype for each karyomorph in each species group was established by comparing the gross chromosome data (RTLs and NF values), C-bands, and Ag-NORs, and it was used for inter-group comparison and testing the present hypothetical groupings.No synapomorphies were found in the fitzingeri group. The status of the andi group is uncertain because only one species was available for study.The bufoniformis group is not closely related to the biporcatus group. The biporcatus series including both the biporcatus and rugulosus groups, each of which is monophyletic is diagnosed by sharing a NOR-correlated constriction in the chromosome pair #10. The 20-chromosome species is inferred to be the most primitive in the rugulosus group, in which the 22- and 24-chromosome species are derived.The present recognized "gollmeri" group is not monophyletic. Eleutherodactylus mimus is the sister group of the rhodopis group. A gollmeri series is proposed for the rhodopis group and the present "gollmeri" group by sharing a fission event of chromosome pair #1 of a rugulosus-like ancestral karyotype. The rhodopis series (sensu Savage, 1987) is no longer recognized.Both biporcatus and gollmeri series are derived from the same fitzingeri-like ancestral karyotype by fusion of the chromosome pairs #9 and #11. Eleutherodactylus greggi was excluded from the "gollmeri" group; the omiltemanus group remains in the "gollmeri " group pending further investigation.Lynch (2000) proposed four morphological synapomorphies for Craugastor, among which only the heavy cranial crests borne laterally on frontoparietal bones for the biporcatus group is confirmed by my chromosome data. The fusion of the eighth and sacral vertebrae in Craugastor is proved to be homoplasious. The fifth toe longer than the third and the strong sexual dimorphism in tympanum size in males cannot be confirmed nor rejected as synapomorphies because of insufficient chromosome data.

Keywords

Biology, Zoology

Link to Full Text

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