Two New Species of Balanophora (Balanophoraceae) From South China

Abstract— Populations of Balanophora from southern China are often identified by local botanists as B. laxiflora based on their long cylindric male inflorescence, subsessile male flowers with slender rudimentary bracts, and subdiscoid synandria. In this study, we clarify the identity of seven such populations based on morphological characters and phylogenetic analysis using nuclear 18S and ITS ribosomal DNA sequences. We confirmed the occurrence of dioecious populations of B. yakushimensis and two previously unrecognized species, which we describe here as B. parajaponica and B. appressa. Phylogenetic analyses indicated that B. parajaponica, B. yakushimensis, B. appressa, B. laxiflora, and the agamospermic B. japonica, formed a well resolved clade, viz. the B. laxiflora clade. The four dioecious species, although highly similar in the morphology of male inflorescence and flowers, can be separated by leaf morphology and arrangement, ovary color, and arrangement of female flowers. The species limit of B. laxiflora, however, remains unresolved.

Sexual antagonism for resistance and tolerance to infection in Drosophila melanogaster

A critical task in evolutionary genetics is to explain the persistence of heritable variation in fitness-related traits such as immunity. Ecological factors can maintain genetic variation in immunity, but less is known about the role of other factors, such as antagonistic pleiotropy, on immunity. Sexually dimorphic immunity—with females often being more immune-competent—may maintain variation in immunity in dioecious populations. Most eco-immunological studies assess host resistance to parasites rather than the host's ability to maintain fitness during infection (tolerance). Distinguishing between resistance and tolerance is important as they are thought to have markedly different evolutionary and epidemiological outcomes. Few studies have investigated tolerance in animals, and the extent of sexual dimorphism in tolerance is unknown. Using males and females from 50 Drosophila melanogaster genotypes, we investigated possible sources of genetic variation for immunity by assessing both resistance and tolerance to the common bacterial pathogen Pseudomonas aeruginosa. We found evidence of sexual dimorphism and sexual antagonism for resistance and tolerance, and a trade-off between the two traits. Our findings suggest that antagonistic pleiotropy may be a major contributor to variation in immunity, with implications for host–parasite coevolution.

Divergence in Defence against Herbivores between Males and Females of Dioecious Plant Species

Defensive traits may evolve differently between sexes in dioecious plant species. Our current understanding of this process hinges on a partial view of the evolution of resistance traits that may result in male-biased herbivory in dioecious populations. Here, we present a critical summary of the current state of the knowledge of herbivory in dioecious species and propose alternative evolutionary scenarios that have been neglected. These scenarios consider the potential evolutionary and functional determinants of sexual dimorphism in patterns of resource allocation to reproduction, growth, and defence. We review the evidence upon which two previous reviews of sex-biased herbivory have concluded that male-biased herbivory is a rule for dioecious species, and we caution readers about a series of shortcomings of many of these studies. Lastly, we propose a minimal standard protocol that should be followed in any studies that intend to elucidate the (co)evolution of interactions between dioecious plants and their herbivores.

Is Silene acaulis (Caryophyllaceae) a trioecious species? Reproductive biology of two subspecies

Based on morphological characters, Silene acaulis subsp. exscapa and Silene acaulis subsp. cenisia have been previously described as dioecious and trioecious, respectively. Here we examine whether these subspecies are truly dioecious (subsp. exscapa) and trioecious (subsp. cenisia) based on individual seed and pollen production. Nine populations of subsp. cenisia and five populations of subsp. exscapa were studied in the French Alps. The ratio of staminate to female plants within populations did not in general differ from 1:1, the sex ratio expected in dioecious populations. Staminate plants of both subspecies were found to set fruits. In subsp.exscapa, the ratio of fruit production in female versus staminate plants is around 900; in subsp. cenisia, this ratio is around 10. The advantage of female plants in fruit production is not always sufficient to explain their frequencies in natural populations. Staminate plants cannot be divided in two distinct categories: males and hermaphrodites. The two subspecies can be best described as subdioecious, although S. a. exscapa is effectively closer to exhibiting true dioecy than S. a. cenisia.Key words: breeding systems, trioecy, subdioecy, Silene acaulis.