MODE OF SEXUAL SELECTION DETERMINED BY RESOURCE ABUNDANCE IN TWO SAND GOBY POPULATIONS

We used field observations and experiments to show that sexual selection in two populations of sand gobies, Pomatoschistus minutus (Pisces, Gobiidae), was affected by differences in resource availability. Male sand gobies rely on empty mussel shells for nest building and spawning. The two populations differed considerably in nest-site abundance and sexual-selection regimes. In one population nest sites were scarce, leading to stronger male-male competition over nests, a higher nest site colonization rate and reduced potential for female choice compared with the other population that had a surplus of nests. In the high-competition population, males were larger than females, perhaps as a response to selection, whereas the other population was not sexually size dimorphic. The results from the field were confirmed in a pool experiment that demonstrated the effect of nest abundance on nest occupancy and male reproductive success. Larger males were more successful in obtaining nest sites in both high and low nest availability treatments. Larger males were also favored by females as mating partners, but only in the treatment with surplus nest sites. Nest shortage was associated with an increased potential for intrasexual selection (measured as the coefficient of variation), whereas the potential for intersexual selection was increased when nests were common. In conclusion, nest-site abundance can influence the relative contribution of intrasexual competition and mate choice in a population. Hence, resource availability can contribute to within-species variation in mating patterns.     

Rediscovery of Cyathus badius,an ‘extinct’ species from the Bonin Islands,Japan

The Bonin Islands, Japan, present a unique and endemic fauna and flora, however a large portion of these species, including fungi, are now considered endangered or extinct. During almost 80 y Cyathus badius was included in that statistics and no additional collections were recorded until a new expedition in 2015. Morphological comparisons with the holotype are consistent with the new specimen, and phylogenetic analyses based on ribosomal ITS, LSU and concatenated dataset placed C. badius in a highly supported clade with C. parvocinereus. Is proposed here to epitypify C. badius with illustrations, new morphological characters and DNA data.     

Outcomes of decades long installation of nest boxes for arboreal mammals in southern Australia

Nest boxes are commonly installed to support hollow‐using species where the abundance of hollow‐bearing trees is deficient. Recent studies have provided equivocal evidence about the effectiveness of nest box projects and have highlighted significant management costs associated with some projects. We document the functionality of 303 nest boxes installed across five different community‐led projects in southern Australia for periods of 10–25 years. As expected, we found that nest boxes lost functionality over time. However, 60% remained functional to support the Brush‐tailed Phascogale (Phascogale tapoatafa) and the Sugar Glider (Petaurus breviceps) after almost 20 years. Years installed, method of nest box attachment and tree species influenced whether boxes remained functional. Nest box construction material changed over time so could not be assessed specifically. When inspected in a single year, the Brush‐tailed Phascogale occupied 9% of functional boxes and another 48% contained their nests. The Sugar Glider occupied 15% of functional boxes and another 22% contained their nests. These values suggest the nest box installations were highly effective for these species, although more detailed study is needed to understand what contribution these installations have made to support the local populations. Maintenance of most nest boxes occurred twice a year in the first five years after installation, but many received no maintenance for periods of three years, and some 10–15 years, before our census. Our findings suggest that infrequent maintenance by community groups can sustain nest box projects over periods of several decades. Research into employing nest boxes as a management tool in Australia is still in its infancy. Further studies are needed to resolve factors that limit their effectiveness.     

Supplemental food alters nest defence and incubation behaviour of an open‐nesting wetland songbird

Climate‐driven increases in spring temperatures are expected to result in higher prey availability earlier in the breeding season for insectivorous birds breeding in wetland habitats. Predation during the incubation phase is a major cause of nesting failure in open‐nesting altricial birds such as the Eurasian reed warbler. The nest predation rate in this species has recently been shown to be substantially reduced under conditions of experimentally elevated invertebrate prey availability. Food availability near the nest may be an important determinant of adult incubation and nest defence behaviours during the incubation period. We used two experimental studies to compare incubation behaviour and nest defence in food‐supplemented and unsupplemented adult Eurasian reed warblers during the incubation phase. In the first study we measured nest defence behavioural responses to a taxidermic mount of a native predator (stoat Mustela erminea). In the second study we used temperature loggers installed in nests to measure breaks in incubation as a measure of nest vulnerability. Food‐supplemented birds responded aggressively to the presence of a predator more quickly than those in the unsupplemented group, suggesting they are closer to their nest and can more quickly detect a predator in the vicinity. Food‐supplemented birds also had shorter breaks in incubation (both in terms of maximum and mean off‐bout durations), presumably because they were foraging for shorter periods or over shorter distances from the nest. This study therefore identifies the behavioural mechanisms by which changes in food availability may lead to changes in nest survival and thus breeding productivity, in open‐nesting insectivorous birds.     

Options for the biological and physical control of Vespa velutina nigrithorax (Hym.: Vespidae) in Europe: A review

Recently, the environmental economist J.M. Salles (Salles, 2016 ) declared that “the Asian hornet was likely to be the most threatening invader insect in France.” Thirteen years after the accidental introduction in France, the Asian hornet (Vespa velutina nigrithorax) has invaded most west European countries. Little has been done to date to limit its progression and its economic, ecological and social impact. Although it is illusory to try to eradicate this species, it is known that a targeted control would limit its threatening trend. Current V. velutina control in France is mainly based on (i) high scale volunteer trapping by citizens and (ii) volunteer spotting of the nest. Evaluation of trapping strategies developed so far to control V. velutina expansion has highlighted their failure and has demonstrated the need to optimize nest detection techniques and to investigate on new control strategies. This review describes most of the means aimed to control predation and expansion of V. velutina, whether they have been scientifically assessed or only tested on field with decent success. Published prospective control methods and biological control techniques are also presented.     

Seasonal spatial dynamics and causes of nest movement in colonies of the invasive Argentine ant (Linepithema humile)

Abstract.  1. Colony organisation and movement behaviour of the Argentine ant ( Linepithema humile ) was studied over 3 years in field populations in California and in captive colonies in the laboratory. This invasive species is highly polydomous and unicolonial; colonies consist of expansive and fluid networks of nests and trails. The spatial and temporal organisation of colonies may contribute to ecological dominance.
2. Argentine ant nests and inter-nest trails shift in size, abundance, and location, so that colony networks are spatially contracted in the winter and expanded spring to autumn. Colonies occupy permanent sites; ants migrated to and from the same winter nest locations year after year, and occupied 30% of the same nests repeatedly during seasonal migrations.
3. Nests were moved on average 2–3 m. Forty-two per cent were occupied less than 1 month, 4% the entire study, and the other 54% lasted 3.9 ± 2.3 months (mean ± SD).
4. Nests were located within 2–4 m of woody plants, in warm sites in the winter and cool sites in the summer. Both humidity and food availability influenced nest-site choice in laboratory colonies. However, when faced with a trade-off between factors, the ants chose humid nest boxes over nest boxes near food, and ants moved nests only in response to changes in humidity and not distance to food.
5. The results indicate that L. humile colonies are seasonally polydomous, and that nest movements are driven by changes in microclimate. Colony organisation maintains high local density and increases food supply, which may improve the competitive ability of L. humile colonies and reduce opportunities for species coexistence.     

Carbon dioxide concentrations in the nests of the mud-dwelling mangrove ant Polyrhachis sokolova Forel (Hymenoptera: Formicidae)

Abstract The nests of the mangrove ant Polyrhachis sokolova are found in soil in intertidal mangrove communities, and are thus inundated at high tides for several hours. Some of the nest galleries are flooded, but others retain air pockets, to which the ants retreat. During and following inundation, we measured carbon dioxide concentrations in air samples collected from different levels in the nests and from artificial 'control' holes in the mud. To account for the relative contribution of different sources of carbon dioxide, we also measured the carbon dioxide production by individual ants (including larvae and pupae) and small samples of mud collected near the ant nests. Nest carbon dioxide concentrations were high (2.5−11%) during and immediately following inundation, but the concentrations in the upper regions of the nest fell as soil water levels receded. However, at depths>10 cm below the level soil surface, the carbon dioxide concentrations remained relatively high and stable (at approximately 2%) over the 11 days between one high tide and the next. The contribution of the mud (and associated microorganisms) to the carbon dioxide concentration in the nests was substantial, and the contribution of the respiration of the ants was approximately 10−15% of the total. The carbon dioxide concentrations in the nests of this species during high tides are among the highest recorded for insect nests, suggesting that these ants may have unusual physiological attributes to match the behavioural and ecological challenges associated with living in the intertidal zone.     

Nesting behavior and breeding success of Hoatzins

ABSTRACT.   Hoatzins ( Opisthocomus hoazin ) are the only member of the family Opisthocomidae and are found only in forests in the Amazon and Orinoco river basin of South America. Although locally common in riparian habitats, information about their natural history is based almost exclusively on observations from gallery forests in the "llanos" (savannahs) of Venezuela. We investigated the nesting activities of Hoatzins in a primary rainforest in Amazonian Ecuador from 1995 to 2000. At our study site, Hoatzins live and breed in the inundated forests that surround lakes and river channels. Egg laying occurred from February to July and from September to November, but always peaked in April, May, and June. The mean clutch size was 2.4 ± 1.1 eggs ( N = 291; range = 1–7), but 51% of all clutches contained two eggs. The mean duration of the incubation period was 32 ± 1.5 d ( N = 20) and, overall, 17% of Hoatzin nests fledged at least one young. The main cause of nest failure was predation, with birds and snakes being the most frequent predators. Hoatzin reproduction was closely linked to the rainy season, and such timing may be influenced by increased food availability (high water levels cause leaf fall and the subsequent growth of new leaves coincides with the beginning of the feeding period of the young) and reduced risk of nest predation by mammalian predators when water levels are high. Our results indicate that the breeding biology of Hoatzins in tropical rainforest habitat, including small clutch sizes and low annual reproductive success, is similar to that of tropical passerines and provides further support for the existence of typical life history characteristics for tropical birds.