Akodon paranaensis Christoff et al.

D’Elía, Guillermo, Mora, Ismael, Myers, Phil & Owen, Robert D., 2008, New and noteworthy records of Rodentia (Erethizontidae, Sciuridae, and Cricetidae) from Paraguay, Zootaxa 1784, pp. 39-57 : 41-46

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) .

Figures

FIGURE 1. Map of Paraguay indicating the localities where the specimens reported here were collected. Locality numbers refer to those of the text.

FIGURE 2. Dorsal, ventral and lateral views of the cranium and mandible of Akodon paranaensis from Paraguay (TK 66278). Scale bar = 5 mm.

FIGURE 3. Partial phylogenetic hypothesis of Akodon (strict consensus of 2 most parsimonious trees: 531 steps; IC = 0.571; IR = 0.568) showing the relationships of cytochrome b haplotypes recovered from specimens assigned to A. paranaemsis and A. reigi. Numbers at nodes indicate jackknife support values. Genbank accession numbers are listed next to species names. Arrows indicate the localities where the specimens were collected. The Paraguayan locality corresponds to locality 1 in Figure 1. * indicates that the sequence was generated in this study.

Tables

TABLE 1. Measurements (mm), weight (gm), and sex of specimens representing new or noteworthy records from Paraguay. Data were taken from specimen tags and field catalogs. TBL, total body length; TL, tail length; HF, hind foot length (including the claw); EL, ear length; W: weight.

Species	Catalog number	sex	TBL	TL	HF	EL	W
Akodon paranaensis	TK 66185	♂	203	95	25	18	39.1 g
A. paranaensis	TK 66278	♂	231	107	29	18	42.4 g
Bibimys chacoensis	GD 153	Ψ	185	80	23	18	40.5 g
B. chacoensis	TK 65978	♂	163	80	21	16	19.2 g
B. chacoensis	TK 66294	♂	161	74	25	16	20.4 g
B. chacoensis	TK 66400	♂	178	81	20	16	24.8 g
B. chacoensis	TK 66401	♂	(132)	(37)	21	16	23.5 g
B. chacoensis	TK 66436	♂	179	76	22	16	33.1 g
B. chacoensis	TK 132621	Ψ	(142)	(35)	21	16	39 g
Oxymycterus misionalis	TK 130587	Ψ	303	135	36	25	121 g
O. misionalis	TK 121751	Ψ	(277)	(132)	35	26	87 g
O. misionalis	TK 121752	♂	(281)	(151)	36	26	140 g
Cerradomys maracajuensis	GD 371	Ψ	378	207	40	21	115 g
C. maracajuensis	GD 372	Ψ	383	206	40	22	120 g
C. maracajuensis	GD 373	Ψ	366	202	39	22	94.5 g
C. maracajuensis	GD 389	Ψ	244	142	31	14	25.5 g
C. maracajuensis	GD 390	♂	396	212	41	22	135 g
Pseudoryzomys simplex	GD 0 65	Ψ	252	132	30	16	38.4 g
P. s i m p l e x	TK 61744	♂	247	128	30	17	38.5 g
Sciurus urucumus	TK 67300	Ψ	467	234	63	33	352 g
Sphiggurus spinosus	GD 252	Ψ	547	214	61	17	1040 g
S. spinosus	UMMZ 174975	Ψ	615	236	58	26	?
Genus Bibimys Massoia
Bibimys chacoensis (Shamel) Fig. 4. Table 1