Akodon paranaensis Christoff et al.

Akodon paranaensis Christoff et al.

Fig. 2. Table 1.

Type Locality: Piraquara (Estacão Ecológica Canguiri), Paraná, Brazil. Distribution: Extreme northeastern Misiones Province in northeastern Argentina, and southeastern Brazil.

New records: 1) ITAPUA, Estancia Parabel, 0.3 km E of houses, 26º 20.91' S 55º 30.75' W, 420 m (TK 66185, TK 66278). Figure 1.

Taxonomy: Akodon is the most diverse genus of Sigmodontinae with around 42 forms currently considered as valid species, and with several more taxonomic forms considered as subspecies or full synonymies of the valid forms (Musser & Carleton 2005). As expected given these numbers, several aspects of the Akodon alpha taxonomy remain confused and poorly addressed. Among them are the distinction of A. paranaensis and A. reigi Gonzalez et al. These two species are very similar morphologically, share the same diploid complement of 2n = 44, show complementary distributions, and are sister to each other in phylogenetic analyses (Fig, 3; see also Gonçalves et al. 2007). Remarkably, in the description of A. paranaensis (Christoff et al. 2000), no comparison with A. reigi was made. Moreover, the same populations in southern Rio Grande do Sul (southern Brazil) were allocated to both species in their original descriptions (Gonzalez et al. 1998; Christoff et al. 2000). Our analysis includes a haplotype recovered from a paratype of A. reigi (MNHNA 3682), but lacks haplotypes from the type locality of A. paranaensis as well as from intermediate areas of Rio Grande do Sul. Therefore, we recognize for the moment both forms as valid species, and since the Paraguayan haplotypes fall in the northern clade (i.e, A. paranaensis; Fig. 3), we allocate the Paraguayan specimens to A. paranaensis. Haplotypes recovered from populations assigned to A. paranaensis (i.e., those from Brazil, northern Argentina, and Paraguay) and to A. reigi (those from Uruguay), which form reciprocally monophyletic groups, differ on average by 5.93 % (observed divergence: range 4.37 – 10.62 %, n=12). Observed variation within A. paranaensis ranges from 1.0 to 9.48 %, while that observed between the available pair of haplotypes of A. reigi is 3.8 %.

Comments: These specimens constitute the first citation of A. paranaensis for Paraguay; which elevates to four the number of Akodon species (A. azarae, A. montensis, and A. toba in addition to A. paranaensis) known for the country (Myers et al. 2002). The Paraguayan records expand to the west the known distribution of A. paranaensis. These specimens were collected in primary tropical forest as well as in secondary forest. Importantly, these records indicate that A. paranaensis also inhabits forested areas, in addition to grasslands.

The specimens reported here were collected in the month of October (1998) and were males with scrotal testes. Other small mammal species collected in the same traplines as the A. paranaensis reported here include the sigmodontines Akodon montensis, Bibimys chacoensis (Shamel), Oligoryzomys nigripes (Olfers), and Thaptomys nigrita (Lichtenstein), and the small didelphid Monodelphis sorex (Hensel).

Type Locality: Las Palmas, Chaco, Argentina.

Distribution: Known from the Argentinean provinces of Chaco, Formosa and Misiones.

New records: ITAPUA: 1) Estancia Parabel, 0.3 km E of house, 26º 20.91' S 55º 30.75' W, 420 m (TK 66294); 2) 3.2 km N, 0.4 km E Ape Aimé 26 32.13' S 54 50.44' W (TK 65978); 3) Estancia Parabel, 5.8 km SW of house (by road), 26º 23.34' S 55º 32.25' W, 360 m (TK 66400, TK 66401, TK 66436); 4) Estancia San Isidro, 5.18 km NW of houses, 26º 29.284' S; 55º 53.803' W (GD 153); 5) Parque Nacional San Rafael 26º 30’ 14.2’’ S 55º 47’ 32.5’’ W, 134 m (TK 132621). Figure 1.

Taxonomy: The genus Bibimys was recently revised by D’Elía et al. (2005). Results of analyses of morphological and molecular geographic variation that included individuals assigned to the three currently recognized species of Bibimys (B. chacoensis, B. labiosus [Winge], B. torresi Massoia) question the distinctiveness of these forms. However, no formal change in the taxonomy of Bibimys species was proposed.

Comments: These records constitute the first formal mention of the genus Bibimys for Paraguay, and the specimens are referred to B. chacoensis. These records partially fill the gap in the previous known distribution of the species, which had been reported from the Argentinean provinces of Chaco and Formosa in the west, and Misiones in the east (D’Elía et al. 2005; Pardiñas & Teta 2005). Field notes available for some of the Paraguayan specimens of Bibimys indicate that they were trapped in small patches of humid grassland near or inside remnants of tropical forest. Four of the specimens were males collected from July to September (1998) that presented scrotal testes. A female collected in January (2007) had a closed vagina, while another collected in November (1999) was lactating and had an open vagina. Other mammal species collected in the same trap lines as the specimens of Bibimys were Akodon montensis, A. paranaensis, Monodelphis sorex, Necromys lasiurus (Lund), Nectomys squamipes (Brants), and Oligoryzomys fornesi (Massoia).