No abstract

In most vertebrates, information from the external environment is used to regulate secretion of gonadotropins and thus time gonadal maturation in anticipation of the breeding season. These environmental factors provide "predictive" information in both the long term (initial predictive) and short term (supplementary), are integrated by the central nervous system, and are then transduced into neuroendocrine and endocrine control components. We apply the constancylcontingency model of predictability to breeding data from several avian species to derive a potential unifying hypothesis to explain how these environmental factors are integrated to regulate gonadal maturation. Predictability (Pr) is a function of varying degrees of constancy (C, the habitat is predictable because it is always the same) or contingency (M, the habitat is predictable in the degree of change from season to season). Thus, although variations in Pr provide useful information for timing gonadal maturation and regression, changes in the contributions of C and M to Pr (i.e., the ratio, M/C) provide even more useful information. It is proposed that the degree to which individuals integrate initial predictive and supplementary information to regulate secretion of gonadotropins, and thus time gonadal maturation and onset of breeding, is a function of the ratio of M to C for any given Pr value. When Pr is not significant (i.e., the environment is unpredictable), then only supplementary factors may be useful for timing breeding. Hypotheses generated by this approach are easily testable. Furthermore, this method could be applied to all vertebrates, and perhaps other organisms, and may provide a unifying framework to investigate the mechanisms by which proximate environmental factors regulate reproductive function in general.

Species of Solanum subgenus Leptostemonum comprise almost one third of the genus and are distributed worldwide. Members of this group are defined by their sharp epidermal prickles; thus, they are commonly referred to as the ''spiny solanums.'' This subgenus includes a number of economically important species such as the Old World eggplants, as well as locally cultivated New World species such as the naranjilla and cocona. Given the size and importance of this group we have examined phylogenetic relationships across subgenus Leptostemonum, including a large sampling of species from previously defined species groups within the subgenus. Evolutionary relationships were inferred using DNA sequence data from two nuclear regions (ITS and the granule-bound starch synthase gene [GBSSI or waxy]) and one chloroplast spacer region (trnS-trnG). Results suggest that Solanum subgenus Leptostemonum is monophyletic when the S. wendlandii and S. nemorense species groups are excluded. We have defined 10 clades within subgenus Leptostemonum, some of which correspond to previously circumscribed species groups or sections. Most of the Old World species of subgenus Leptostemonum belong to a single species-rich clade. Sharp prickles and/or stellate hairs evolved more than once in Solanum, and floral heterandry originated multiple times within the ''spiny solanums.''

Despite intensive morphological and molecular studies of Onagraceae, relationships within the family are not fully understood. One drawback of previous analyses is limited sampling within the large tribe Onagreae. In addition, the monophyly of two species-rich genera in Onagreae, Camissonia and Oenothera, has never been adequately tested. To understand relationships within Onagraceae, test the monophyly of these two genera, and ascertain the affinities of the newly discovered genus Megacorax, we conducted parsimony and maximum likelihood analyses with rbcL and ndhF sequence data for 24 taxa representing all 17 Onagraceae genera and two outgroup Lythraceae. Results strongly support a monophyletic Onagraceae, with Ludwigia as the basal lineage and a sister-taxon relationship between Megacorax and Lopezia. Gongylocarpus is supported as sister to Epilobieae plus the rest of Onagreae, although relationships within the latter clade have limited resolution. Thus, we advocate placement of Gongylocarpus in a monogeneric tribe, Gongylocarpeae. Most relationships within Onagreae are weakly resolved, suggesting a rapid diversification of this group in western North America. Neither Camissonia nor Oenothera appears to be monophyletic; however, increased taxon sampling is needed to clarify those relationships. Morphological characters generally agree with the molecular data, providing further support for relationships.

We infer phylogenetic relationships among Lycium, Grabowskia, and the monotypic Phrodus microphyllus, using DNA sequence data from the nuclear granule-bound starch synthase gene (GBSSI, waxy) and the chloroplast region trnT-trnF. This is the first comprehensive molecular phylogenetic study of tribe Lycieae (Solanaceae). In addition to providing an understanding of evolutionary relationships, we use the phylogenetic hypotheses to frame our studies of breeding system transitions, floral and fruit evolution, and biogeographical patterns within Lycieae. Whereas Lycium is distributed worldwide, Phrodus and the majority of Grabowskia species are restricted to South America. Tribe Lycieae is strongly supported as monophyletic, but Lycium likely includes both Grabowskia and Phrodus. Results also suggest a single dispersal event from the Americas to the Old World, and frequent dispersal between North and South America. The diversity of fruit types in Lycieae is discussed in light of dispersal patterns and recent work on fruit evolution across Solanaceae. Dimorphic gender expression has been studied previously within Lycium, and results indicate that transitions in sexual expression are convergent, occurring multiple times in North America (a revised estimate from previous studies) and southern Africa.