Morphometric differentiation between Neotropical black-eared opossums, Didelphis marsupialis and D. aurita (Didelphimorphia, Didelphidae) by R. CERQUEIRA 1 and B. LEMOS 12 ? 1 Laboratorio de Vertebrados, Departamento de Ecologia, Universidade Federal do Rio de Janeiro, RJ, Brazil E-mail :lab\'erl@btologia. ufrj. br : Divisäo de Genetica, Institute National de Cancer, Praga da Cruz Vermellia, 23, 6" Andar, 20230-130, Rio de Janeiro, RJ, Brazil E-mail:lemosb@biologia. ufrj. br ' Departamento de Genetica, IB, UFRJ Summary. - The Neotropical black-eared opossums comprise two allopatric species that are restricted to forested habitats : Didelphis aurita occurring from northern Argentina to the Nor- theast of Brazil, mostly along the Atlantic rainforest but also at Araucaria highlands, and D. mar- supialis which occurs mostly within the Amazonian rainforest. Their status as separate species or allopatric subspecies has been a matter of debate. We provide an analysis of the morphometric differences between D. aurita and D. marsupialis based on eigheteen cranium measurements. An ANOVA between sexes showed sexual dimorphism with males consistently larger than females in both species. Hence, sexes were treated separately. ANOVA between D. aurita and D. marsu- pialis showed that they are significantly different for 14 and eight characters of females and males, respectively. D. aurita and D. marsupialis were also readily separated by discriminant analysis that correctly classified more than SO % of the specimens. The squared Mahalanobis dis- tances were slightly higher than five at both sexes. Despite the lack of obvious qualitative mor- phological characters distinguishing D. aurita and D. marsupialis, our results show that they are morphometrically diagnosable and should be considered separate species. Resume. - Les opossums ä oreilles noires neotropicaux sont represented par deux especes allopatriques limitees a des habitats de foret: Didelphis aurita, repartie depuis le nord de Argentine jusqu'au nord-est du Bresil, surtout le long de la foret atlantique, mais aussi sur les plateaux a Araucarias ; D. marsupialis qui se trouve surtout dans la foret d'Amazonie. Leur Statut d'especes ou de sous-especes allopatriques a ete le sujet de debats. Dans ce travail nous donnons une analyse des differences morphometriques entre D. aurita et D. marsupialis en utilisant 18 mensurations du crane. Une ANOVA entre sexes a mis en evidence 1'existence d'un dimor- phisme sexuel, les males etant plus grands que les femelles dans les deux formes. Les sexes ont done ete traites separement. Une ANOVA entre D. aurita et D. marsupialis a montre que les deux especes sont significativement differentes pour 14 caracteres de femelles et 8 caracteres de males. D. aurita et D. marsupialis sont aussi immediatement separees par une analyse discrimi- nante qui a permis de reconnaitre correctement plus de 80 % des specimens. Les carres des dis- tances de Mahalanobis ont ete legerement superieurs ä cinq pour les deux sexes. Malgre Fabsence de caracteres morphologiques qualitatifs qui distinguent D. aurita de D. marsupialis, nos resultats montrent qu'ils sont morphometriquement identifiables et doivent etre considered comme deux especes distinctes. KEY WORDS : Didelphis marsupialis, D. aurita, taxonomy and morphometry. Mammalia, t. 64, n° 3, 2000: 319-327. Brought to you by | CENTRO DE INVESTIGACIÓN Y DOCENCIA ECONÓ Authenticated | 187.33.65.87 Download Date | 6/7/13 4:12 AM