Vol. 56, 2017 (update: 2017.5.31) Patterns of Differentiation and Disparity in Cranial Morphology in Rodent Species of the genus Megadontomys (Rodentia: Cricetidae)Rachel M. Vallejo1,3, José Antonio Guerrero2,*, and Francisco X. González-Cózatl3 doi:10.6620/ZS.2017.56-14 1División de
Posgrado, Instituto de Ecología, A. C. Xalapa, Veracruz, México.
E-mail: rachel@uaem.mx (Received 12 September 2016; Accepted 9 May 2017; Communicated by Benny K.K. Chan) Rachel
M. Vallejo, José Antonio Guerrero, and Francisco X. González-Cózatl
(2017) The genus Megadontomys
is a Mexican endemic group of rodents with allopatric populations
occurring in fragmented patches of cool-humid forest. In this study we
used geometric morphometrics methods to assess patterns of
morphological variation and differentiation in skull and mandible among
and within species of the genus. ANOVA showed that sexual dimorphism
was significant for skulls size (P
< 0.01) but not for mandibles, and MANOVA indicated that both
structures did not differ in shape between sexes. ANOVA reveled a
significant difference among the three species (P < 0.01), M. nelsoni exhibit the largest
skull. Canonical variate analyses and Goodall’s test found differences
in both skulls and mandibles shape among species, being M. cryophilus and M. thomasi the most divergent. The
comparison between phylogroups within M.
thomasi also revealed significant differences in shape for both
structures. Disparity assessment showed that M. thomasi is the species that
contributed the most to the overall shape disparity (51.80% for skull
and 38.29% for mandible). The permutation test of phylogenetic signal
in morphometric data was significant for the skull but not for the
mandible. Morphometric data support the recognition of three
morphotypes whitin the genus. The sister species M. nelsoni and M. thomasi displayed a grater shape
similarity in the skull and mandible shape between them. In contrast, M. cryophilus exhibited the
greatest shape divergence relative to the other species. The
morphological evidence supports the existence of the two different
phylogroups within M. thomasi,
supporting their recognition as Evolutionary Significant Units
previously suggested on molecular data. The lack of phylogenetic signal
in the mandible corresponds with the environmental plasticity of this
structure as compared with the skull. Key words: Disparity, Evolutionary history, Geometric morphometrics, Megadontomys, Morphological differentiation. *Correspondence: E-mail: aguerrero@uaem.mx Citation: Vallejo RM, Guerrero JA,
González-Cózatl FX. 2017. Patterns of differentiation and disparity in
cranial morphology in rodent species of the genus Megadontomys (Rodentia:
Cricetidae). Zool Stud 56:14.
doi:10.6620/ZS.2017.56-14. |