Species of the genus Eurydema (Hemiptera: Heteroptera: Pentatomidae) in Far East Asia: An integrated approach using morphological, molecular, and data crossing analyses for taxonomy

In a revision of four previously described species of the genus Eurydema in Far East Asia, we confirm only two species, one of which consists of two subspecies: E. dominulus (Scopoli 1763) [= E. pulchra (Westwood 1837), syn. nov.], E. gebleri gebleri Kolenati 1846, and E. gebleri rugosa Motschulsky 1861 [stat. nov.]. In order to prove the above taxonomic changes, we focused on three major analyses; (1) morphological study (color patterns), (2) molecular identification (DNA barcording) and (3) cross–breeding (inter–specific copulation, fertilization). The results of these analyses were sufficient to confirm the new taxonomic changes. According to the cross–breeding analysis, interspecific copulation between males of E. dominulus (= E. pulchra) and females of E. g. gebleri or E. g. rugosa occurs in nature, but the eggs laid by the interspecific copulation were unfertilized. Two subspecies, E. g. rugosa and E. g. gebleri, preserve their own unique coloration patterns; this was confirmed by the results of intra–subspecific copulation and breeding. However, the 1 st progeny from the inter–subspecific copulation of E. g. rugosa♂ X E. g. gebleri♀ (or E. g. gebleri♂ X E. g. rugosa♀) were confirmed to have the coloration patterns inherited from E. g. gebleri.

Asymmetric reproductive isolation during simultaneous reciprocal mating in pulmonates

The generality of asymmetric reproductive isolation between reciprocal crosses suggests that the evolution of isolation mechanisms often proceeds in reciprocal asymmetry. In hermaphroditic snails that copulate simultaneously and reciprocally, asymmetry in premating isolation may not be readily detectable because the failure of the symmetric performance of courtship would prevent copulation from occurring. On the other hand, through their prolonged copulation, snails discriminate among mates when exchanging spermatophores for their benefit and thus may exhibit asymmetric reproductive isolation during interspecific mating. However, no clear case of reciprocal asymmetry has been found in reproductive isolation between snail species. Here we show a discrete difference in hybridization success between simultaneous reciprocal copulations between two species of pulmonate snails. Premating isolation of Bradybaena pellucida (BP) and Bradybaena similaris (BS) is incomplete in captivity. In interspecific copulation, BP removes its penis without transferring a spermatophore, while BS sires hybrids by inseminating BP. Thus, ‘male’ BP or ‘female’ BS rejects the other individual, while female BP and male BS accept each other, so that the two sexes of either BP or BS oppose each other in mate discrimination. Our results are a clear example of asymmetry in reproductive isolation during simultaneous reciprocal mating between hermaphroditic animals.

Analyse expérimentale de l'isolement reproductif entre deux espèces jumelles et sympatriques d'araignées : le Lycosa thorelli (Keyserling) et le Lycosa carbonelli Costa et Capocasale

Four experimental groups were used: (A) males Lycosa thorelli × female L. thorelli; (B) male Lycosa carbonelli × female L. carbonelli; (C) Male L. thorelli × female L. carbonelli; (D) male L. carbonelli × female L. thorelli. Males were placed in a field with conspecific sexual pheromone and confronted to anesthetized virgin females. Male L. thorelli showed a greater tenacity than male L. carbonelli in the maintenance of the copulatory position. The typical copulation pattern (intraspecific groups) became atypical in interspecific groups. Only one typical interspecific copulation was observed in group C. Male L. carbonelli showed a good specific discrimination when mounting the female, while male L. thorelli showed a low discrimination level. The maintenance of the copulatory position could be determined by a modal number of ejaculations in the case of male L. carbonelli and by a modal duration in the case of male L. thorelli. Atypical copulations might indicate a mechanical incompatibility between the genitalia of the two species. Typical copulations produced offspring, indicating the absence of postcopulatory isolation mechanisms.

Interspecific copulation in and co-occurrence of similar-sized freshwater centropagid copepods

Laboratory experiments were performed in which males of a given centropagid calanoid copepod species were placed with females of another species. Five interspecific pairings were tested, and in four of these, males attempted copulation or copulated with the partner of a different species. Metasome lengths of copepods in all populations used for experiments were determined: males attempted copulation with females whose average length was 0.88-1.09 times the normal size of the female for that species. These results imply that co-occurrence of similar-sized calanoids may be rare because of mating behaviour, temporal or spatial differences in mating, rather than because of competition for resources. A survey of reported co-occurrences of centropagid copepods in the genera Boeckella and Calamoecia found in Australia supports this contention.

Definition and revision of the Enoplognatha ovata (Clerck) group (Araneae: Theridiidae)

The monophyletic Enoplognatha ovata group is defined on the basis of the following synapomorphic characters: subapical first metatarsal trichobothrium, sclerotized and modified apex of the conductor in the male palpal bulbus, and strongly developed copulatory pockets in the female vulva. In the group the male conductor and the female epigynal openings together with the copulatory pockets form a coadapted functional unit which might prevent interspecific copulation. The hitherto known range of the group covers the western Palaearctic and, apparently through recent introduction by man, the eastern and western Nearctic. Three species are included: E. ovata (Clerck) (Palaearctic, Nearctic), E. latimana n. sp. (southern Middle Europe, Nearctic) and E. penelope n. sp. (Mediterranean). The characteristics of the species are described and discussed both at the individual and population levels.

An Analysis of Copulatory Behaviour of Microtus Agrestis and M. Arvalis in Relation To Reproductive Isolation

A quantitative description of the copulatory behaviour of two species of closely related voles (M. agrestis and M. arvalis) is presented. Special attention is paid to the separate contributions of males and females to the time course of events in order to make predictions about the problems which would arise in interspecific copulation attempts. The species were similar with regard to mounting latency, number of ejaculations and durations of pauses between mounting series after ejaculation. Durations of mounting series were shorter in M. agrestis than in M. arvalis. The duration of a series is determined by the number and length of intermount intervals (IMIs) and nonejaculatory mounts and duration of the ejaculatory mount. The number of mounts was greatest and their duration was shortest in M. arvalis, leading to equal total mounting time in the two species. IMIs were longest in M. arvalis and, because the number was also greatest in M. arvalis, the total IMI time per series was longest in M. arvalis. Consequently, the mounting series was longest in M. arvalis. Durations of mounts were exponentially distributed; therefore, the tendency of males and females to terminate mounts could be estimated as constants. In both species, females showed a much higher tendency to terminate mounts than did males. In M. arvalis, both males and females showed higher termination tendencies than in M. agrestis. Males of the two species did not differ in their tendencies to terminate IMIs. Females of M. arvalis, however, aggressively resisted mounting more often than did M. agrestis females, leading to relatively long IMIs in M. arvalis. M. agrestis males often ejaculated during a single mount; M. arvalis males did so after at least five mounts. In accord with this species difference, it could be shown that mount terminations (or the experiences connected with them) negatively influenced the excitation state of M. agrestis males; i.e., the number of mounts prior to an ejaculation was greater (and the total mounting time was longer), the shorter the time the mounts lasted (i.e., the higher the females termination tendency was). In M. arvalis the number of mounts was smaller, the shorter the mounts lasted. In this species, high termination tendencies of the female correlated with much resistance to mounting (long IMIs). The combination of short mounts with long IMIs seems to have a positive influence upon the males. Thus, M. agrestis females delay ejaculation by a high termination tendency of mounts, whereas M. arvalis females seem to accelerate ejaculation by similar actions. Males and females appear to be very well adapted to each other: the M. agrestis female is relatively tolerant and the male ejaculates sooner, the more tolerant she is; the M. arvalis female is rejective and the male ejaculates sooner the more rejective she is, at least within the limits of rejectivity of the observed females. Females differ such that rejectivity in M. agrestis equals tolerance in M. arvalis, so that interspecific copulations are not likely to be successful. It is hypothesized that the rejectivity in M. arvalis fits in with the gregarious way of life of this species. For the female may select the fittest males and/or rejectivity by the female and the positive effect of it upon the male may serve as an incest preventing mechanism.