No cultural transmission of species recognition between parents and offspring in free-living great tits and blue tits

Imprinting plays a key role in the development of species recognition, with young imprinting upon the morphological characters of their parents. However, the potential role that cultural transmission might play in species recognition remains largely uninvestigated. Great tits (Parus major) and blue tits (Cyanistes caeruleus) do not normally perceive each other as sexual competitors or potential partners. However, after reciprocal interspecific cross-fostering, both species may perceive individuals of the foster species as potential rivals or mates. Although the experience of being raised by heterospecifics clearly has affected the species recognition of cross-fostered birds, some of them breed naturally with conspecifics. The offspring of such cross-fostered birds (OCF) are hence raised by parents that look like ordinary conspecifics but display deviant species recognition as compared to controls in terms of aggressive response towards rivals. Comparing the aggressive behavior of OCF, cross-fostered birds and controls towards territorial intruders may thus help tease apart the influence of morphological vs behavioral cues of parents in the development of offspring species recognition. To this end, we compared birds from all three treatments with respect to their aggressive response to territorial intruders of both species during the breeding season. OCF and controls did not differ in their pattern of response towards heterospecific and conspecific stimuli. Compared to cross-fostered birds, OCF and controls showed less aggression towards heterospecific intruders, while the response towards conspecific intruders did not differ between treatments. These results demonstrate that both tit species imprint on the morphological characters of their parents, but that parental behavior is not important for the development of species recognition in terms of aggressive response towards territorial intruders.     

Delayed dispersal as a potential route to cooperative breeding in ambrosia beetles

Xyleborini are a species-rich tribe of ambrosia beetles, which are haplodiploid and typically mate among siblings within their natal brood chamber. Several characteristics of this tribe would predict the evolution of higher levels of sociality: high genetic relatedness within galleries due to inbreeding, high costs of dispersal and the potential benefit of cooperation in brood care within the natal gallery (e.g. by fungus gardening, gallery extension, offspring feeding and cleaning). However, information on the social system of these beetles is very limited. We examined the potential for cooperative breeding in Xyleborinus saxeseni by monitoring dispersal in relation to brood size and composition. Results show that adult female offspring delay dispersal despite dispersal opportunities, and apparently some females never disperse. The females’ decision to stay seems to depend on the presence of eggs and dependent siblings. We found no indication that female offspring reproduce in their natal gallery, as colonies with many mature daughters do not contain more eggs than those with few or no daughters. There is a significant positive relationship between the number of females present and the number of dependent siblings (but not eggs), which suggests that cooperative brood care of female offspring raises colony productivity by improving survival rates of immatures. Our results suggest that cooperative breeding is likely to occur in X. saxeseni and possibly other xyleborine species. We argue that a closer look at sociality within this tribe may yield important information on the factors determining the evolution of cooperative breeding and advanced social organization.     

The role of different types of detached macrophytes in the food and habitat choice of a surf-zone inhabiting amphipod

Allorchestes compressa is the dominant macroinvertebrate species in wrack accumulations on surf zones of south-western Australia. These amphipods were provided with a choice of macrophyte material representing brown and red algae and seagrass in a series of preference experiments in the laboratory and field. Feeding experiments showed that A. compressa exhibited a strong preference for particular types of macrophytes (P < 0.01). Amphipods primarily consumed brown algae, with 69–98% of the biomass of Ecklonia radiata and 64% of the biomass of Sargassum sp. lost over the experiments. This study has shown that the amphipod A. compressa exhibits a clear preference for brown algae over red algae and seagrass as food. In terms of habitat preference, tank experiments using a series of pair-wise comparisons showed that, in the absence of fish predators, A. compressa selected seagrass as its preferred habitat over the other types of wrack (P < 0.001). When satiated or starved, between 68 and 83 and 79 and 98% of amphipods were found in Amphibolis and Posidonia, respectively. In contrast, field-cage experiments revealed that A. compressa preferred either mixed wrack, brown algae or red algae over seagrass as a habitat (P < 0.01). The contrasts between results from the laboratory and field suggest that other factors such as the presence of predators, water flow and light could influence habitat choice in the surf zone. This study shows that allochthonous material transported to surf zones from other habitats therefore play different roles in driving secondary production in this shoreline habitat.     

Genetic structure of leopard shark (<Emphasis Type="Italic">Triakis semifasciata</Emphasis>) populations in California waters

The leopard shark (Triakis semifasciata) is an important predator in coastal marine ecosystems of California, targeted by recreational and commercial fishermen and of specific interest in fisheries management. From October 2003 to August 2006, 169 leopard sharks were collected from the coast of California (between 40.750°N and 32.678°N) and analyzed for mitochondrial and nuclear genetic structure. Analyses of mtDNA control region sequences revealed relatively low levels of genetic variation (five haplotypes, average pairwise divergence π = 0.0067). In contrast, leopard sharks were highly polymorphic for inter simple sequence repeats (ISSRs), which characterize a broad range of the nuclear genome. The null hypothesis of panmixia in California waters was rejected for both genetic markers, and ISSRs displayed a statistically significant pattern of isolation by distance (IBD) across the species range (P = 0.002). A variety of analyses showed that divergence is most pronounced in the northernmost population of Humboldt Bay. Natal philopatry in T. semifasciata was tested using Siegel-Tukey tests on data partitioned by breeding site status, and sex-specific philopatry was tested by comparing IBD plots between sexes. Although there was some evidence for natal philopatry in leopard sharks (P = 0.038), and population divergence may be related to the proximity of breeding sites (P = 0.064), we found no support for sex-specific philopatry. In addition to identifying a novel set of highly variable genetic markers for use in shark population studies, these results may be used to better inform management decisions for leopard sharks in California.     

The influence of resource specialization on the response of reef fish to coral disturbance

Ecological theory predicts that habitat generalists are less prone to decline or extinction in response to habitat disturbance than habitat specialists. One mechanism that may afford habitat generalists greater persistence is their ability to successfully emigrate from degrading environments. This study compared the response of habitat specialist and generalist reef fish species to live coral disturbance. In replicate coral colonies, live coral was experimentally degraded (low, medium and high coral loss). Species continued residence within the colonies was then surveyed over time. In addition, the ability of habitat generalist and specialist species to migrate between degraded (100% loss) and live coral colonies was compared. Habitat specialists exhibited a higher propensity to remain in colonies with low levels of coral loss. However, there was no significant difference between specialist and generalist species in continued residence in habitats with either medium or high levels of coral loss; both functional groups showed low levels of residence. In terms of migration success, generalists moved further than specialists and showed higher levels of successful migration over the majority of distances examined. The influence of habitat specialization on the behavioral response to coral loss may be a useful predictor of changes to coral reef fish communities in response to coral disturbance.     

Hydroquinones from defensive secretion of a giant Pacific millipede, <Emphasis Type="Italic">Acladocricus setigerus</Emphasis> (Diplopoda: Spirobolida)

Summary. The presence of considerable quantities of hydroquinones including hydroquinone, 2-methylhydroquinone, 2,3- dimethoxyhydroquinone, 2-methoxy-3-methylhydroquinone, and 2,3-dimethoxy-5-methylhydroquinone renders the defensive secretion of Acladocricus setigerus (Silvestri, 1897) significantly different from that of other quinone-producing millipedes. In addition, two hitherto undescribed compounds, namely, 2,3-dimethoxy-5-methylhydroquinone and 2-methyl-3,4-methylenedioxyphenol, were characterized from the defensive secretion. However, it is uncertain if the latter compound is formed after the release of the secretion. The two major compounds, 2-methyl-1,4-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone, constitute about 75% of the defensive fluid. Furthermore, hydrocarbons, which are typically present in the secretions of most other arthropods that use benzoquinones as repellents, are notably absent in the secretion of A. setigerus.     

Small-scale spatial and temporal interactions among benthic crustaceans and one fish species in the Bay of Biscay

In the summer of 2004, a video survey was carried out in the northern part of the central mud bank (Grande Vasière) of the Bay of Biscay to study the small scale relationship between the dominant crustacean megafauna Nephrops norvegicus, Munida rugosa and Goneplax rhomboides and juvenile hake (Merluccius merluccius). Using a towed body, high-resolution videos were recorded in six sampling sites. Statistical modelling using generalised additive models (GAM) revealed variations in activity patterns for two species. More N. norvegicus were observed outside their burrows at dawn and somewhat at dusk (no observations during night) while G. rhomboides was less observed in the morning. In addition, reduced spatial overlap between G. rhomboides and N. norvegicus suggested reduced competition for food but also space as both are burrowing species. The observed temporal and spatial activity patterns may contribute to regulating assemblage structure as competing species may be actively foraging at different times and locations thus reducing direct competition.     

The effect of salinity on survival,bioenergetics and predation risk in the mud crabs <Emphasis Type="Italic">Panopeus simpsoni</Emphasis> and <Emphasis Type="Italic">Eurypanopeus depressus</Emphasis>

The effect of salinity on survival, bioenergetics and predation risk was studied in two common mud crabs in the Gulf of Mexico, Eurypanopeus depressus and Panopeus simpsoni. Eurypanopeus survived better at low salinities (the 28-day LC₅₀ of E. depressus was 0.19 PSU compared with 6.97 PSU for P. simpsoni). While low salinity increased energy expenditure and reduced food consumption and absorption, resulting in lower scope for growth, identical responses to salinity occurred in both species. Both species also had similar salinity-dependent patterns of hyper-osmoregulation. Because these physiological mechanisms could not explain differences between the two species in salinity tolerance, we explored the effect of salinity on competition for refugia. Eurypanopeus had higher resource holding potential for refugia, especially at low salinity. As a consequence it had lower predation risk to blue crabs in laboratory experiments. The higher tolerance by E. depressus for low salinities, and greater resource holding potential for refugia may explain why it has a more euryhaline distribution than P. simpsoni.     

Assessment of patch quality by ladybirds: relative response to conspecific and heterospecific larval tracks a consequence of habitat similarity?

Summary. Aphid colonies can reach high levels of abundance but last for short periods of time. The larvae of aphidophagous ladybirds (Coleoptera: Coccinellidae) that feed on these colonies might therefore suffer from starvation, which favours the occurrence of cannibalism and intraguild predation. Thus, the assessment of patch quality becomes crucial and it has been shown that female ladybirds refrain from laying eggs in the presence of an oviposition deterring semiochemical deposited by their larvae. Adalia bipunctata (L.), Adalia decempunctata (L.) and Coccinella septempunctata L. are 3 sympatric species of ladybirds, which can co-occur in aphid colonies. As a consequence, their eggs and larvae are under threat, not only from cannibalism but also intraguild predation. Females should, therefore, also use the tracks deposited by heterospecific larvae to assess the quality of aphid colonies as oviposition sites. The expectation is that: 1- the strength of the reaction to each other’s larval tracks should be correlated with percentage habitat overlap and that 2- the reaction to conspecific larval tracks should be stronger than to heterospecific tracks. In order to test these hypotheses, females’ oviposition behaviour was analysed and a chemical analysis of the tracks of their larvae undertaken. The results show that oviposition behaviour is not related to habitat overlap. Both species of Adalia react to tracks of their own larvae and those of C. septempunctata, but A. decempunctata reacted more strongly than A. bipunctata. C. septempunctata reacted very slightly to its own tracks but not to those of either species of Adalia. The larval tracks are mainly composed of alkanes. Those of the two species of Adalia are qualitatively 100% similar and 60% so when the quantitative results are compared. They are, however, only 24–29% similar to those of Coccinella septempunctata.     

A method to reconstruct anguilliform fishes from partially digested items

Estimating the amounts of resources consumed by individuals is important in many studies. For predators, allometric relationships can be used to extrapolate the size of preys from undigested remains found in the stomach and in the faeces. However, such equations are available for a limited number of species. Based on a large sample size gathered in New Caledonia on both predators (sea kraits) and their preys (anguilliform fishes), we provide the first allometric relationships that allow estimating accurately the mass and the size of various anguilliform fish species.