Grammostola

Iheringia. Série Zoologia
Print version ISSN 0073-4721

Iheringia, Sér. Zool. vol.96 no.1 Porto Alegre Mar. 2006
http://dx.doi.org/10.1590/S0073-47212006000100013

Reproductive isolation among three populations of the genus Grammostola from Uruguay (Araneae, Theraphosidae)
Aislamiento reproductivo entre tres poblaciones del género Grammostola de Uruguay (Araneae, Theraphosidae)

RodrigoPostiglioni; Fernando G. Costa Laboratorio de Etología, Ecología y Evolución, Instituto de Investigaciones Biológicas Clemente Estable, Av. Italia 3318, Montevideo, Uruguay. (posti@iibce.edu.uy)

ABSTRACT Ethological isolation of individuals from three allopatric Grammostola populations of Uruguay, G. iheringi(Keyserling, 1891), G. mollicoma (Auserer, 1875) northern population and G. mollicomasouthern population, was tested under laboratory conditions. Grammostola iheringi behaved as a reproductive isolated species, whereas the two populations of G. mollicoma did not show ethological isolation between them. However, ecological isolating reproductive mechanisms could be acting on G. mollicoma populations. Artificial burrows seem to be important for reproductive isolation in thesespecies. Keywords: Grammostola iheringi, Grammostola mollicoma, reproductive isolation, ethological isolation.

RESUMEN Se testeó bajo condiciones de laboratorio, el aislamiento etológico de individuos de poblaciones alopátridas deGrammostola de Uruguay, G. iheringi (Keyserling, 1891), G. mollicoma (Auserer, 1875) población norte y G. mollicoma población sur. Grammostola iheringi se comportó como unaespecie aislada, mientras que las dos formas de Grammostola no mostraron aislamiento etológico. Sin embargo, mecanismos de aislamiento reproductivo ecológico podrían estar actuando entre las poblaciones de G. mollicoma. Las cuevas artificiales serían importantes para el aislamiento reproductivo de estas especies. Palabras-clave: Grammostola iheringi, Grammostola mollicoma, aislamiento reproductivo,aislamiento etológico.

Although studies on reproductive biology of araneomorph spiders were widely developed during the past century (FOELIX, 1996), reports on mygalomorphs in general and particularly on the large theraphosids (commonly known as tarantulas), are scarce (review in COSTA & PÉREZMILES, 2002). The genus Grammostola comprises species of large bodied tarantulas (20 - 30 mm carapacelength). Two allopatric species have had their reproductive biology studied in Uruguay: G. iheringi (Keyserling, 1891), which have been reported only at neighboring areas of the Quebrada de los Cuervos, province of Treinta y Tres (35°57'S, 54°31'W), and G. mollicoma (Auserer, 1875) which is widely distributed throughout the country (COSTA & PÉREZMILES, 2002;Fig. 1). Two allopatric populations ofG. mollicoma are found (Fig. 1), one in northern and other in southern Uruguay (although the limits between these two populations are not clearly defined). Moreover, there are some morphological differences between individuals from the two populations. In the southern population, individuals have a round-shaped abdomen, are brown-colored and have long, red hairs located ventrally on coxae, femora,and patellae of the pedipalps and legs. Conversely, individuals from the northern population have an oval abdomen, are black-colored and lack those red hairs on pedipalps and legs. Recently collected individuals of the southern population living at the North of Río Negro river (Fig. 1) suggest that zones close to latitude 33°10'S and not the Río Negro river basin would be the limit of northernand southern populations. These data would support the occurrence of two different spider species. However, previous preliminary reports had found no ethological isolation between these populations in laboratory open arenas (PÉREZ-MILES & COSTA, 1992). This contradiction needs to be elucidated with more data.

On the other hand, the only known population of G. iheringi from Uruguay is located...