Isozyme criteria in the testing of phyletic relationships between species of Gobius and related eastern Atlantic-Mediterranean genera (Teleostei: Gobüdae)

Horizontal starch gel electrophoresis was employed to investigate allozyme variation at 19 isozyme loci, in nine closely-related Atlantic-Mediterranean gobiid fish species, to assess genetic relationships, and to compare this with a phyletic hypothesis based on morphological apo-morphies. The species examined were Gobius niger, G. auratus, G. cruentatus, G. paganellus, Mauligobius maderensis, Zosterisessor ophiocephalus, Thorogobius ephippiatus, Padogobius martensii and P. nigricans . Various phenetic and cladistic analyses were performed on isozyme and morphological data. The phenetic and cladistic results from morphological data, and the cladistic results from isozyme data, were largely comparable, with P. martensü and P. nigricans forming a sister group to all the other taxa, species of Cobius forming a crown group within the latter, and stem lines formed by Mauligobius, Zosterisessor and Thorogobius , respectively. The isozymic estimates of genetic distance differed from these chiefly in the relative positions of Zosterisessor and G. auratus , which appear less similar to other species of Gohius. G. auratus shows many alleles which are unique within the genus Gobius ; possible explanations for this are put forward. The position of nigricans as congeneric with Padogobius martensü is confirmed by both phenetic and cladistic analyses of isozyme data.     

Life-history studies versus genetic markers – the case of Hylochares cruentatus (Coleoptera, Eucnemidae)

Recent findings in the greater Helsinki region of Hylochares cruentatus (Coleoptera, Eucnemidae), previously considered locally extinct, have shown ecological and morphological differentiation from H. cruentatus found in Russian Karelia. Despite their identical genetic constitution, differences in adult morphology, male genitalia as well as greatly differing life-history traits between the Finnish and Russian beetles prompted recognizing the Russian Hylochares as a distinct, new species: Hylochares populi n.sp., type locality Russia, Karelia, Kuganavalok. Single old specimens from Estonia and the Altai Mountains belong to the same taxon. Traditional morphological characters and life-history traits separate the two taxa, whereas the four applied genetic markers were identical, suggesting very recent diversification. The Russian H. populi lives in large soft-wooded aspen trees; H. cruentatus prefers tree- and bush-sized willows with harder wood. Conservation actions have to change focus from aspen trees to willow habitats to secure the survival of this rare beetle species in Finland.     

Geographical patterns of genetic divergence in the widespread Mesoamerican bumble bee Bombus ephippiatus (Hymenoptera: Apidae)

Bumble bees (Bombus Latreille) are an important group of social insects, well recognized throughout northern temperate regions as important pollinators of wild and agricultural plants. Little is known about the biology of this group in southern portions of the Americas, especially in Mesoamerica, a region of geological and ecological complexity from Mexico through Central America. One ubiquitous Mesoamerican species, Bombus ephippiatus, is enigmatic. Like many other Bombus, this species is homogeneous in body structure yet exhibits striking intraspecific color pattern polymorphism across its range, leading to uncertainty about its genealogical boundaries. It has been grouped taxonomically with B. wilmattae, a species narrowly restricted to southern Mexico and northern Guatamala. Furthermore, the relationships between these two taxa and a third species, B. impatiens, found only in America north of Mexico, have been controversial. Our phylogenetic analysis of DNA sequences from mitochondrial COI and nuclear PEPCK and CAD resolves the phylogeny of these three taxa as (B. impatiens, (B. ephippiatus, B. wilmattae)). Additional data from eight nuclear microsatellite markers reveal complex patterns of genetic divergence and isolation among populations of B. ephippiatus across its extensive geographic range, providing evidence for multiple independent evolutionary lineages. These lineages correspond not only to geographic and habitat variation across their range, but also to distinct color pattern groups present in the species. Knowledge of the phylogeny and genetic divergence of the B. ephippiatus group will provide a framework for understanding evolutionary and ecological origins of color pattern polymorphism in bumble bees, as well as providing insight into geographical factors enhancing speciation in Mesoamerica.     

Female choice and male reproductive success in the angel blenny,Coralliozetus angelica (Teleostei: Chaenopsidae)

Correlates of reproductive success of male Coralliozetus angelica were studied in field populations in the central Gulf of California by collecting males with their shelters (vacant barnacle tests) and counting the number of eggs defended. Male body size was positively correlated with the number of eggs defended. This apparently resulted from female preference for large males since females preferred to mate with the larger of two males in laboratory choice experiments. Condition of males, as assessed by their relative head width, was also positively correlated with the number of eggs defended. Fit of males in their shelter entrance, male colour intensity, and male size relative to immediately surrounding males were not correlated with reproductive success. The quality of shelters was an important determinant of male reproductive success since females apparently avoided mating with males in heavily fouled shelters. Large shelters tended to be more heavily fouled than small shelters and male size and shelter size were positively correlated. The resulting negative correlation of male size and shelter quality apparently constrained female preference for large males and may be an important factor limiting the degree of polygyny in this species.     

Shelters and their use by fishes on fringing coral reefs

Coral reef fish density and species richness are often higher at sites with more structural complexity. This association may be due to greater availability of shelters, but surprisingly little is known about the size and density of shelters and their use by coral reef fishes. We quantified shelter availability and use by fishes for the first time on a Caribbean coral reef by counting all holes and overhangs with a minimum entrance diameter ≥3 cm in 30 quadrats (25 m(2)) on two fringing reefs in Barbados. Shelter size was highly variable, ranging from 42 cm(3) to over 4,000,000 cm(3), with many more small than large shelters. On average, there were 3.8 shelters m(-2), with a median volume of 1,200 cm(3) and a total volume of 52,000 cm(3) m(-2). The number of fish per occupied shelter ranged from 1 to 35 individual fishes belonging to 66 species, with a median of 1. The proportion of shelters occupied and the number of occupants increased strongly with shelter size. Shelter density and total volume increased with substrate complexity, and this relationship varied among reef zones. The density of shelter-using fish was much more strongly predicted by shelter density and median size than by substrate complexity and increased linearly with shelter density, indicating that shelter availability is a limiting resource for some coral reef fishes. The results demonstrate the importance of large shelters for fish density and support the hypothesis that structural complexity is associated with fish abundance, at least in part, due to its association with shelter availability. This information can help identify critical habitat for coral reef fishes, predict the effects of reductions in structural complexity of natural reefs and improve the design of artificial reefs.     

A western Scottish population of the leopard-spotted goby, Thorogobius ephippiatus (Lowe) (Teleostei: Gobioidea)

A population of the sublittoral leopard-spotted goby, Thorogobius ephippiatus (Lowe, 1839), is recorded from Upper Loch Torridon, Scotland, and the more northerly occurrence of this Mediterranean-Atlantic species along western Scottish coasts confirmed. Modified methods of capture are described. Distinctive systematic features of this population, which tends to have low sensory papilla and pectoral ray values, are examined with reference to other T. ephippiatus and the related T. macrolepis (Kolombatovic, 1891). The time of onset and reasons for this local differentiation are discussed.     

Effects of breeding site density on competition and sexual selection in the European lobster

The availability of breeding sites has been predicted to affectthe intensity of sexual selection, including mate competition,mate choice and ultimately, variation in mating success. Wetested the hypothesis that reduced density of shelters wouldcause an increase in the intensity of sexual selection in Europeanlobsters, Homarus gammarus. However, we found little supportfor our predictions. For example, within-sex competition bymales and by females was not more intense when shelters werescarce. Indeed, females attempted to evict one another fromshelters significantly more often when shelters were common.When shelters were abundant, shelter-holding males had greatermating success than males without shelters, yet females didnot show more interest towards these males during courtshipencounters. Mate attraction was more strongly related to largemale body size when shelters were scarce. Overall, the resultssuggest that reduced shelter density does not lead to more overtwithin-sex aggression in this species. Instead, we suggest thatimpacts of breeding resource availability on sexual selectionmay depend on the range over which resources are measured, withextreme scarcity of shelters rendering overt competition uneconomical.Furthermore, females may become more selective of male traitssuch as large size, which enhance male control of breeding sitesand hence protection of females.     

Agonistic behaviour and control of access to hiding places in two intertidal blennies, Lipophrys pholis and Coryphoblennius galerita (Pisces: Blenniidae)

In this study we investigated the relationships between dominance rank and access to shelters in captive groups of Lipophrys pholis and Coryphoblennius galerita, as well as the effects of group size and shelter availability. Dominance rank was strongly correlated with size in juvenile L. pholis and with sex and size in adult C. galerita, males being dominant over females of similar size. Access to shelters was significantly correlated with dominance rank. For both species, most interactions occurred out of shelters. Direct disputes over shelters were always initiated by the dominant fish and the initiator was always the winner. The rate of aggression per fish per unit time decreased with an increase in the number of fish in L. pholis but not in C. galerita. No significant differences were found in groups differing in the number of shelters. C. galerita showed a higher rate of agonistic interactions and a higher proportion of overt aggression than L. pholis. It is suggested that one of the functions of agonistic interactions in these fishes is the control of a set of shelters, in the network of pathways used by each individual within its home range, minimising the time required to hide in case of danger. Received in revised form: 29 January 2001 Electronic Publication     

To mate or not to mate,and subsequent host search by a haplodiploid female parasitoid wasp

Mated females of haplodiploid species can vary the sex ratio of their offspring, but virgin or sperm‐depleted females can produce only males. Depending on the costs and benefits, the theory of constrained sex allocation states that female haplodiploids may vary in their propensity to mate, with important implications for the populations’ sex ratio. Unmated female parasitoid wasps Alabagrus texanus (Braconidae) have been observed to reject matings with males, even under highly confined spatial conditions. We performed field trials to determine whether unmated female A. texanus would mate. We then compared the preferences of the resulting unmated (constrained) and mated (unconstrained) female wasps for shelters constructed and occupied by their hosts, fern moth caterpillars Herpetogramma theseusalis (Crambidae) on fern fronds. We presented the wasps with pairs of shelters collected from the field that differed in size, as well as freshness, fern species, and presence or absence of caterpillars. Unconstrained females searched small shelters more frequently than did constrained females and tended to favor senesced (old) shelters over fresher ones. They did not differ in choice between shelters on marsh and sensitive ferns or between shelters containing caterpillars and empty shelters. The preference for small shelters by the unconstrained wasps may enhance their rate of contacting favorable hosts, but the foraging regime of the constrained females should expose them to caterpillars at sites infrequently searched by the unconstrained females.     

Diel activity and reproductive territory of the Japanese bagrid catfish, <Emphasis Type="Italic">Pseudobagrus ichikawai</Emphasis>

The endangered Japanese bagrid catfish, Pseudobagrus ichikawai, is typically nocturnal, emerging from shelters, such as crevices along the shore, at sunset to actively forage in open areas throughout the night with short-term movements of up to 40 m (except for mature males). Just before sunrise, individuals return to their shelters, from which they rarely emerge in daytime. Mature males (3 years-of-age or older) are found only in the vicinity of their shelters of during both day and night, which they defend with strong territorial behaviour. The restricted reproductive resources (shelters) probably severely limit the population size and reproduction in this species.     

Does shelter enhance early seedling survival in dry environments? A test with eight Mediterranean species

Question: Do solid‐walled polyethylene tubes and mesh fabric tubes improve the short‐term survival of eight Mediterranean tree and shrub species often used in the restoration of arid environments? Location: We conducted two experimental plantations in degraded field sites in the province of Almería (SE Spain), under arid Mediterranean conditions. Methods: One‐year‐old seedlings of Ceratonia siliqua, Juniperus phoenicea, Olea europaea, Pinus halepensis, Pinus pinaster, Quercus coccifera, Quercus ilex and Tetraclinis articulata were planted either sheltered by one of the above shelter tubes, or by being left unsheltered. Survival was recorded the first growing season after planting, which was a very dry season. Results: Overall, seedling survival ranged from as little as 0% to 24%, and tree shelters consistently enhanced survival in Quercus species only, ranging from 16% in walled shelters to 8% in mesh shelters. Shelters failed to boost survival in the six remaining species. Conclusion: The results of this study suggest that both walled and mesh shelters were mostly ineffective at increasing seedling survival for the Mediterranean species used in this experiment; these species coincide with those used in restoration programs. The use of shelters in restoration programs conducted in arid environments should be reconsidered, while walled shelters might be advisable for Mediterranean Quercus species only. Further research is necessary to develop and assess improved types of shelters for arid environments.     

Indirect interactions mediated by leaf shelters in animal–plant communities

Leaf shelters indirectly mediate interactions in animal–plant communities by providing the occupants with several kinds of benefits, as physical ecosystem engineering. The occupants benefit from favorable microhabitat, reduction in antiherbivore defense, and protection from natural enemies. The primary shelter maker has to spend energy and time and producing silk, but shelter users have great advantages without incurring costs. Shelter users consist of a wide range of arthropod taxa and can be divided into two groups: coexisting organisms that live with a primary shelter maker in the same shelter, and secondary users, which inhabit a leaf shelter after it is utilized by a shelter maker. Leaf shelters mediate interactions between (1) primary shelter makers and coexisting organisms or (2) primary shelter makers and secondary users, (3) secondary users, (4) shelter users and their natural enemies, and (5) primary shelter makers, secondary users, and their host plants. Most interactions between primary shelter makers and coexisting organisms constitute a direct trophic linkage rather than indirect ones. There are actually unidirectional beneficial effects from a primary shelter maker to secondary shelter users, whereas leaf shelters mediate competition and predation among shelter users. By providing a leaf shelter, a shelter maker leads to increased diversity of interactions. Leaf shelters modify the distribution of organisms on the host plant and influence herbivory on the host plant. In tritrophic interactions, leaf shelters act as cues for natural enemies that search for a shelter user as prey. Furthermore, by enhancing habitat heterogeneity, leaf shelters affect the abundance and species richness of arthropods on host plants. Received: July 24, 2000 / Accepted: February 15, 2001     

Why be a rewarding trap? The evolution of floral rewards in Arum (Araceae), a genus characterized by saprophilous pollination systems

Plant species of the genus Arum typically have lure-and-trap pollination systems that are saprophilous (i.e. attracting flies or beetles searching for breeding sites in decaying organic matter). They have been assumed to always attract and trap their pollinators by deception because the inflorescences provide unsuitable breeding grounds for pollinators. The present study explored the possibility that one species, Arum creticum Boiss. & Heldr., which has yellow, sweet-smelling inflorescences, rewards its pollinators and that this increases its success in attracting pollinators over its close relative, Arum idaeum Coust. & Gadoger. The relationship between rewards provided, floral structure, insect attraction, and pollen import and export was examined in two naturally occurring sympatric populations of A. creticum , A. idaeum , and their natural hybrids. The results showed that plants providing more pollen were visited by larger numbers of females of a mining bee Lasioglossum marginatum Brullé as well as adults and nymphs of a hemipteran bug Dionconotus cruentatus creticus Heiss. In A. creticum , L. marginatum was found to be a better outcrossing vector than D. cruentatus in areas where both pollinators occurred because L. marginatum individuals carried more pollen on their bodies and travelled greater distances between inflorescences, thus increasing the potential for outcrossing. The finding that floral rewards may result in increased fitness, compared to nonrewarding systems that rely on attracting saprophilic pollinators, suggests that it is possible for rewarding species to evolve from saprophilous systems.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 257–268.     

Positive and negative effects of leaf shelters on herbivorous insects: linking multiple herbivore species on a willow

We experimentally examined the effects on other herbivorous insects of leaf shelters constructed by lepidopteran larvae on a willow, Salix miyabeana. Several insect species occupied the vacant leaf shelters. Our experiment using artificial leaf shelters showed that the number of aphids increased with the number of artificial leaf shelters on a shoot, as did the numbers of three ant species ( Camponotus japonicus, Lasius hayashi, and Myrmica jessensis) that entered leaf shelters to collect aphid honeydew. To determine the ant-mediated effect of leaf shelters on herbivorous insects that do not use leaf shelters, we transferred newly hatched larvae of a common leaf beetle, Plagiodera versicolora, to the leaves of shoots with and without artificial leaf shelters. One day after the transfer, larval survival rate was significantly lower on shoots with shelters than on those without shelters, and shoots with shelters had significantly more ants than did shoots without shelters. Our field experiments demonstrated clearly that shelter-making lepidopteran larvae increased the abundance of both aphids and ants and decreased the survival rate of leaf beetle larvae, probably because the larvae were removed by ants that were attracted to the leaf shelters by the aphid colonies.     

Avian predation on ringed seal Phoca hispida pups

Summary Ringed seals, Phoca hispida, born in exposed situations are killed by glaucous gulls, Larus hyperboreus. The small size of ringed seals adapted to giving birth in snow shelters makes them especially vulnerable to avian predators when born outside the lair. This might be one of the important factors in limiting the southern range of breeding in this seal species.     

Resting environments of some Costa Rican mosquitoes

The resting sites of tropical American mosquitoes are poorly documented, and the few reports that do exist are largely from opportunistic collections. Since blood‐engorged females (used in determining host associations) are more efficiently collected from resting sites than attractive traps, information on resting site utilization has practical value. To investigate differences in the resting sites utilized by tropical mosquitoes, we collected and identified female mosquitoes from one man‐made (resting shelter) and three natural (buttress tree roots, hollow trees, and understory vegetation) resting environments at a tropical dry forest location in western Costa Rica. All of the most common species collected demonstrated associations with one or more resting environments. Females of five species (blood‐engorged Anopheles albimanus, Uranotaenia apicalis, Uranotaenia lowii, Uranotaenia orthodoxa, and blood‐engorged Mansonia titillans) were collected in significantly greater numbers from understory vegetation than other resting environments. Culex erraticus and other members of the subgenus Melanoconion were encountered more often in resting shelters, hollow trees, and buttress roots, while Culex restrictor (blood‐engorged) females were associated with hollow trees. Similarity indices indicate that buttress tree roots, hollow trees, and resting shelters are similar with respect to the mosquito communities that utilize them as resting sites, while understory vegetation has a resting fauna that is different than the other environments surveyed here. These results add to the body of information regarding resting sites utilized by tropical American mosquitoes.     

Unusual morphological and ecological characteristics of hyperbenthic juveniles of Gobius cruentatus

Unidentified hyperbenthic gobiid juveniles were collected while SCUBA diving at Oštro, in the Kvarner area, northern Adriatic Sea from 1996 to 2000. An additional 23 specimens of this form were collected at Oštro on 13 May 2002. They were kept alive and reared in the aquarium. Groups of specimens were sacrified periodically to study changes in morphology and growth. From the data acquired the hyperbenthic juveniles were identified as those of the red‐mouthed goby Gobius cruentatus . The present findings provide data on the unusual morphology and ecology of G. cruentatus juveniles.     

Seed dormancy,soil type and protective shelters influence seedling emergence at Shark Bay,Western Australia: Insight into global dryland revegetation

Seedling emergence is a major constraint on dryland revegetation success. In this study, we investigated seedling emergence of six framework shrub species as influenced by seed treatment, soil type and protective shelters using a large field trial in arid Western Australia. We observed the main effects of seed treatment and soil type to account for the majority of the variation in emergence. For species that exhibit pronounced dormancy, we found emergence of dormancy‐alleviated or treated (T) seed to be significantly greater than dormant or untreated (UT) seed, with responses varying across species (e.g. 41 times greater for Acacia ligulata Benth., and 10 times greater for Stylobasium spathulatum Desf.). For shallowly or nondormant species like Senna glutinosa (DC) Randall, UT seed emergence was slightly greater than for T seed. Compared to subsoil, topsoil was more receptive to infiltration (3.44 vs. 0.38 mm/min), and less prone to compaction (1.24 vs. 1.67 g/cm³) and crusting (0.6 vs. 1.3 kg/cm²); however, subsoil had greater moisture retention. Shelters failed to benefit soil moisture retention in either soil type, but enhanced emergence for most species. This study provides insight into how various cost‐effective treatments can be utilized to manipulate seed dormancy to optimize seedling emergence, the intrinsic value of topsoil as a superior growth medium and the benefit of novel, low‐cost shelters for enhancing seedling emergence. In arid environments, sowing T seed in combination with UT seed increases the likelihood of capitalizing on inherently variable precipitation events.