Pollen-ovule relation in Adesmia tristis and reflections on the seed–ovule ratio by interaction with pollinators in two vertical strata

The vertical distribution of pollinators is an important component in the foraging pattern of plants strata, and it influences the reproductive system (pollen/ovule ratio) and seed/ovule ratio. Niches in two different strata from Adesmia tristis Vogel were evaluated in these aspects. This plant is an endemic shrub from the Campos de Cima da Serra in Southern Brazil. The studies were carried out from January 2010, to January 2011, at Pró-Mata/PUCRS (Catholic University of Rio Grande do Sul) (29°27'-29°35'S and 50°08'-50°15'W), São Francisco de Paula, sate of Rio Grande do Sul, Brazil. Breeding system of A. tristis is mandatory allogamy. The vertical profile in A. tristis has differentiated foraging niches among the most common pollinators. Bees of Megachile genus forage in the upper stratum, and representative bees of the Andrenidae family explore the lower stratum. The upper stratum of the vertical profile had more contribution to seed production. Adesmia tristis showed evidence of pollination deficitA distribuição vertical dos polinizadores é um importante componente no padrão de forrageamento nos estratos das plantas e influencia o sistema reprodutivo (relação pólen/ óvulo) e a razão semente/óvulo. Nichos em dois estratos diferentes de Adesmia tristis Vogel foram avaliados quanto a esses aspectos. Essa planta é um arbusto endêmico dos campos de Cima da Serra no Sul do Brasil. Os estudos ocorreram de janeiro de 2010 a janeiro de 2011, no Pró- Mata/PUCRS (Pontifícia Universidade Católica do Rio Grande do Sul) (29°27'-29°35'S e 50°08'-50°15'W), São Francisco de Paula, estado do Rio Grande do Sul, Brasil. O sistema reprodutivo de A. tristis é alogamia obrigatória. O perfil vertical em A. tristis possui diferentes nichos de forrageamento entre os polinizadores mais comuns. Abelhas do gênero Megachile forrageiam no estrato superior e as abelhas representantes da família Andrenidae exploram o estrato inferior. O estrato superior do perfil vertical contribui mais na produção de sementes. Adesmia tristis apresentou evidências de déficit de polinizaçã

Chromosomal variability and evolution in the tribe Phyllotini (Rodentia, Cricetidae, Sigmodontinae)

Sigmodontinae is a group of rodents with a rich and complex diversification in South America. Among them, the tribe Phyllotini comprises at least ten genera and exhibits high chromosome variability. It was proposed that chromosome evolution in mammals is influenced by centromeric meiotic drive (CMD). This mechanism of chromosome transmission generates a bimodal distribution of karyotypes, which are either mostly acrocentric or mostly biarmed. Here, we reviewed and analyzed chromosome data from Phyllotini to contrast them with that predicted by the CMD model. Additionally, we analyzed the chromosome data in a phylogenetic framework. When only one karyotype was considered per polymorphic species, the distribution resembles the CMD model, although it is not completely bimodal. The position of most polymorphic species in the center of the distribution and the presence of XY1Y2 chromosomes in a species with exclusively biarmed autosomes suggested that the CMD model is applicable to some particular species. Within a phylogenetic framework, some genera are characterized by high fundamental numbers (FNs), such as Calomys, Phyllotis, and Andalgalomys, and others by low FN (Loxodontomys, Auliscomys). This suggests that FN is a good marker for inferring some intra- and intergeneric relationships. However, the chromosome data are not coincident with the close molecular relationship obtained between Andalgalomys and Salinomys, because these species have respectively the maximum and minimum diploid number (2n) found in the tribe. There are 87 described karyotypes, but only one species has 2n�=�52, considered ancestral for sigmodontines, or 2n�=�70, proposed as ancestral for phyllotines. This suggests a major chromosomal restructuring at the base of the phyllotine radiation.Fil: Lanzone, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Cardozo, Dario Elbio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Sanchez, Denisse Mavis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Marti, Dardo Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Ojeda, Ricardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin