Are generalist Aphidiinae (Hym. Braconidae) mostly cryptic species complexes?

Aphidiinae are mostly composed of specialist parasitoids and the few species described as generalist are suspected to be composed of cryptic specialists, almost indistinguishable based on morphological characteristics. The use of molecular markers has proven to be a useful tool for revealing cryptic species complexes and here we use seven mitochondrial and nuclear gene fragments to study possible genetic differentiation among seven Aphidiinae generalists. Maximum likelihood (ML) trees and Bayesian Poisson tree processes (bPTP) models were conducted on each gene separately and on the seven genes together. The standard cytochrome c oxidase I barcode region appeared to be the most polymorphic and probably the best marker to reveal putative cryptic species. However, we showed with ML trees and bPTP models that a complementary use of mitochondrial and nuclear genes was the most relevant approach to reliably identify cryptic genetic clades in the Aphidiinae. Overall, most of the analysed generalist morphospecies were shown to be composed of subgroups related to the aphid host, some of them revealed as cryptic species by the species delimitation analysis. Further studies are needed to reveal the generality of this result in Aphidiinae.     

NITROGEN EXCRETION IN MARINE AND FRESH-WATER CRUSTACEA

1. The major characteristic of aquatic Crustacea is ammonotelism as shown by the relative importance of various nitrogenous end-products of their nitrogen metabolism.
2. In contrast to urico- and ureo-genesis pathways, ammoniogenesis pathways have received recent attention; some specific enzymes such as glutamate dehydrogenase, AMP-deaminase and glutaminase are now admitted to play a possible key role in ammoniogenesis of various crustacean species.
3. Processes involved in ammonia output through the gill epithelium (diffusion and/or ionic exchanges) are discussed though few data related to Crustacea are as yet available compared to those obtained in ammonotelic fishes.
4. The effects of some environmental factors as well as the physiological state of animals on nitrogen excretion of Crustacea are envisaged. The effects of temperature, salinity and NH₄ concentration in the external medium are discussed first, followed by the changes in nitrogen excretion associated with the moult cycle, the nutritional state of animals and possible neuroendocrine control. It is demonstrated that the response of the excretion rate to these factors presents various patterns according to the species, its osmoregulatory abilities and its body reserves. Changes can also occur in the requisite metabolic pathways, thus increasing the difficulty of generalization.
5. In spite of the great diversity encountered within Crustacea an attempt to bring out general trends of their nitrogen excretion is proposed.
6. The present review is focused on metabolic and physiological aspects of crustacean nitrogen excretion but the significance of nitrogen release in nutrient regeneration in marine and fresh-water ecosystems is foreseen.     

Morphological reinforcement,ancient introgressive hybridization and species delimitation in African stem‐borer species of the genus Sesamia Guenée (Lepidoptera: Noctuidae)

Species delimitation, an issue central to systematics and biodiversity studies, is addressed in the epunctifera group of the stem borer genus Sesamia Guenée (Lepidoptera: Noctuidae). This group is composed of four sub‐Saharan species: Sesamia poephaga Tams & Bowden; Sesamia epunctifera Hampson; Sesamia penniseti Tams & Bowden; and Sesamia poebora Tams & Bowden, the taxonomic status of which was unclear. The first species was considered a possible synonym of the second, and the third species was considered a possible synonym of the fourth. An analysis combining morphological, ecological and molecular data enables us to conclude that S. epunctifera and S. poephaga are different species, and that S. poebora is a synonym of S. penniseti. Two new species were discovered: Sesamia firmata sp.n. and Sesamia veronica sp.n. Sesamia firmata sp.n. has atypical genitalic morphology, suggesting a strong selection resulting in a reinforcement of pre‐zygotic isolation. Some specimens previously identified as S. penniseti on the basis of morphology are sisters to S. epunctifera on the mitochondrial tree, and are connected to S. penniseti on the nuclear tree. The mitochondrial distance from S. penniseti and S. epunctifera is 7.6% and 3.9%, respectively, suggesting an ancient mitochondrial introgression from S. epunctifera into S. penniseti. The possible causes of the reinforcement and introgressive hybridization are discussed. This case of mitochondrial introgression, uncommon in Lepidoptera, in which females are the heterogametic sex, may be an exception to Haldane's rule. The hybrid is assigned the rank of species and named Sesamia pennipuncta sp.n.