Single Habitat Research Articles

Global network of specific virus–host interactions in hypersaline environments

Hypersaline environments are dominated by archaea and bacteria and are almost entirely devoid of eukaryotic organisms. In addition, hypersaline environments contain considerable numbers of viruses. Currently, there is only a limited amount of information about these haloviruses. The ones described in detail mostly resemble head-tail bacteriophages, whereas observations based on direct microscopy of the hypersaline environmental samples highlight the abundance of non-tailed virus-like particles. Here we studied nine spatially distant hypersaline environments for the isolation of new halophilic archaea (61 isolates), halophilic bacteria (24 isolates) and their viruses (49 isolates) using a culture-dependent approach. The obtained virus isolates approximately double the number of currently described archaeal viruses. The new isolates could be divided into three tailed and two non-tailed virus morphotypes, suggesting that both types of viruses are widely distributed and characteristic for haloarchaeal viruses. We determined the sensitivity of the hosts against all isolated viruses. It appeared that the host ranges of numerous viruses extend to hosts in distant locations, supporting the idea that there is a global exchange of microbes and their viruses. It suggests that hypersaline environments worldwide function like a single habitat.

Avifaunal inventory of the Amazonian savannas and adjacent habitats of the Monte Alegre region (Pará, Brazil), with comments on biogeography and conservation

Knowledge of the avifaunal composition of Amazonian savannas is important in facilitating a greater understanding of the patterns of evolution of the regional biota. Despite this, this vegetation type has been poorly sampled in comparison to adjacent rainforest habitats. The aim of this paper is to provide an avifaunal inventory of the savannas and other adjacent habitats of Monte Alegre, on the left bank of Amazon River, northwestern Pará, Brazil. Our survey is based both on our own fieldwork and on previously-collected specimens deposited in museums. A total of 300 bird species have been recorded in the region. Ninety-four species (31.3%) were restricted to a single habitat type, indicating that habitat heterogeneity is important to the overall species richness. Despite the fact that the Monte Alegre savannas present typical species restricted to this habitat, several open-country birds that occur in larger savanna areas located on the borders of Amazonia (along the Atlantic coast and close to the ‘cerrado’ boundaries) were not recorded in this area. Although Monte Alegre is species impoverished relative to other savanna regions in the Amazon basin, the Monte Alegre savannas shelter the Sulfur-breasted Parakeet (Aratinga maculata), a vulnerable species in Pará state that is only known from the Guianan area of endemism (Aleixo et al., 2011). We also comment on biogeography, taxonomy, noteworthy records, natural history and conservation of the regional avifauna.

Microhabitat specialization of tropical rain-forest canopy trees in the Sovi Basin, Viti Levu, Fiji Islands

Abstract:Island biotas often have lower species diversity and less intense competition has been hypothesized as a result. This should result in lower habitat specificity compared with mainland habitats due to larger realized niches. We investigate microhabitat associations of canopy trees with regard to differences in topography on an oceanic island (Viti Levu, Fiji) using twenty 10 × 60-m plots. We find high tree-species diversity (112 species with dbh ≥ 10 cm in a total of 1.08 ha) and high endemism (c. 60%), compared with other islands in Western Polynesia. Our sample plots aggregate into three distinct groups that are mostly defined by micro-topography: (1) ridges and steep slopes (well-drained sites), (2) moderate slopes and ridge flats (moderate drainage), and (3) flats (poor drainage). Associations with microhabitat are found for more than 50% of the 41 most common species but only one species is apparently restricted to a single habitat. These findings are similar to other rain forests and demonstrate considerable niche differentiation among island rain-forest tree species.

An integrated analysis into the causes of ungulate mortality in the Wanda Mountains (Heilongjiang Province, China) and an evaluation of habitat quality

As part of our ungulate population protection program, the specific causes of ungulate mortality were examined and the effect of single habitat on habitat selection by ungulate analyzed. An integrated occurrence–mortality model for three ungulate species (wild boar Sus scrofa L ., red deer Cervus elaphus L . and roe deer Capreolus capreolus Pallas) within the Wanda Mountains of Heilongjiang Province, China was then created. Results showed that steel cable snares and poison, used to kill ungulates, were the primary threats to survival of wild boar (40.07% poison, 27.79% cable snares), red deer (51.35% poison, 40.54% cable snares) and roe deer (29.31% poison, 56.90% cable snares). Furthermore, we found evidence that aspect, slope, elevation and forest type are important factors in determining ungulate habitat preference. The integrated occurrence–mortality model indicated that 46.39% of suitable habitat was associated with mortality risk. This model correctly classified 8.06% (297.49 km 2) of the study area as unsuitable habitat, 5.43% (200.44 km 2) as first attractive sink-like habitat, 32.76% (1209.85 km 2) as second attractive sink-like habitat, 8.20% (302.77 km 2) as third attractive sink-like habitat, and 8.91% (329.00 km 2), 30.53% (1127.22 km 2) and 6.11% (225.29 km 2) as first, second and third source-like habitats, respectively. The results indicate that source-like habitats should be preserved to prevent habitat loss and degradation, while attractive sink-like habitats should be managed effectively to mitigate mortality risks. In particular, the various authorities need to be more proactive (increase patrolling, thereby providing employment, educational opportunities and increasing income) to reduce human-caused ungulate mortality.

The cultural niche: Why social learning is essential for human adaptation

In the last 60,000 y humans have expanded across the globe and now occupy a wider range than any other terrestrial species. Our ability to successfully adapt to such a diverse range of habitats is often explained in terms of our cognitive ability. Humans have relatively bigger brains and more computing power than other animals, and this allows us to figure out how to live in a wide range of environments. Here we argue that humans may be smarter than other creatures, but none of us is nearly smart enough to acquire all of the information necessary to survive in any single habitat. In even the simplest foraging societies, people depend on a vast array of tools, detailed bodies of local knowledge, and complex social arrangements and often do not understand why these tools, beliefs, and behaviors are adaptive. We owe our success to our uniquely developed ability to learn from others. This capacity enables humans to gradually accumulate information across generations and develop well-adapted tools, beliefs, and practices that are too complex for any single individual to invent during their lifetime.

How unique is the tiger beetle fauna (Coleoptera, Cicindelidae) of the Balkan Peninsula?

The tiger beetle fauna of the Balkan Peninsula is one of the richest in Europe and includes 19 species or 41% of the European tiger beetle fauna. Assembled by their biogeographical origins, the Balkan tiger beetle species fall into 14 different groups that include, Mediterranean, Middle Oriental, Central Asiatic, Euro-Siberian, South and East European, Pannonian-Sarmatian, West Palaearctic, Turano-European and Afrotropico Indo-Mediterranean species. The Mediterranean Sclerophyl and the Pontian Steppe are the Balkan biogeographical provinces with the highest species richness, while the Balkan Highlands has the lowest Cicindelidae diversity. Most species are restricted to single habitat types in lowland areas of the Balkan Peninsula and only Calomera aulica aulica and Calomera littoralis nemoralis occur in respectively 3 and 4 different types of habitat. About 60% of all Balkan Cicindelidae species are found in habitats potentially endangered by human activity.

To Be Seen or to Hide: Visual Characteristics of Body Patterns for Camouflage and Communication in the Australian Giant CuttlefishSepia apama

It might seem obvious that a camouflaged animal must generally match its background whereas to be conspicuous an organism must differ from the background. However, the image parameters (or statistics) that evaluate the conspicuousness of patterns and textures are seldom well defined, and animal coloration patterns are rarely compared quantitatively with their respective backgrounds. Here we examine this issue in the Australian giant cuttlefish Sepia apama. We confine our analysis to the best-known and simplest image statistic, the correlation in intensity between neighboring pixels. Sepia apama can rapidly change their body patterns from assumed conspicuous signaling to assumed camouflage, thus providing an excellent and unique opportunity to investigate how such patterns differ in a single visual habitat. We describe the intensity variance and spatial frequency power spectra of these differing body patterns and compare these patterns with the backgrounds against which they are viewed. The measured image statistics of camouflaged animals closely resemble their backgrounds, while signaling animals differ significantly from their backgrounds. Our findings may provide the basis for a set of general rules for crypsis and signals. Furthermore, our methods may be widely applicable to the quantitative study of animal coloration.

A Diversity of Moths (Lepidoptera) Trapped with Two Feeding Attractants

AbstractFeeding attractants for moths are useful as survey tools to assess moth species diversity and for monitoring of the relative abundance of certain pest species. We assessed the relative breadth of attractiveness of two such lures to moths, at sites with varied habitats during 2006. Eighty-six of the 114 species of Lepidoptera captured were in traps baited with acetic acid plus 3-methyl-1-butanol (AAMB), a moth lure that is based on the odor chemistry of fermented molasses baits. Fifty-two of the 114 species were trapped with a floral odorant lure comprised of phenylacetaldehyde, β-myrcene, methyl salicylate, and methyl-2-methoxy benzoate. Preference for one lure type was statistically supported for 10 species of moths: seven to the AAMB lure and three to the floral lure. To gain better information on lure preference, 10 pairs of traps baited with the same lures were maintained in a single habitat type (riparian) during 2008. Sixty-eight of 89 species captured were in traps baited with AAMB, and 43 were in traps baited with the floral lure. Preference for a lure type was statistically supported for 39 of the 89 species of moths trapped; 32 to the AAMB lure and seven to the floral lure. Both of these lures hold advantages for trapping different types of moths, and both lures might be used in a complementary way to sample moth biodiversity.

Human altered ecosystems: suitable habitats as well as ecological traps for dragonflies (Odonata): the matter of scale

Habitat loss and degradation can be considered as major threats to freshwater invertebrates. These often irreversible processes lead to reduction of habitat patch quality and cause local extinctions of dragonflies, notably of habitat specialists. However, the biodiversity of specific secondary habitats is very high. Here, we present findings from a 10-year study that intensively monitored odonate fauna in the Upper Silesian industrial coal region having many secondary habitats characterized by very frequent disturbances due to soil instability. We evaluated qualitative changes in the dragonfly assemblages on 10 patches using a modified dragonfly biotic index. Data analysis was supplemented by a model examining population dynamics of the threatened dragonfly Leucorrhinia pectoralis, using the capture-mark-recapture method, as an effective indicator of habitat quality. We show that dynamics of environmental conditions in secondary habitats are reflected in population dynamics of dragonfly populations and assemblages. As frequency of L. pectoralis population extinctions within the patch is considerable and independent of size and spatial isolation of single habitats, these can be regarded as ecological traps. Nevertheless, the metapopulation dynamics may be a key adaptation of dragonflies to frequent freshwater habitat disturbances. We suggest that local extinctions are effectively balanced with (re-)colonization of newly emerging freshwater habitats. These findings have implications for potential conservation management of specific human-made habitats, because secondary habitats with a great diversity of succession stages arising directly as a consequence of environmental instability may be considered as partial alternatives to natural habitats in cultural landscapes.

Species-area and species-sampling effort relationships: disentangling the effects

Species numbers tend to increase with both the area surveyed (species–area relationship, SAR) and the number of samples taken (species–sampling effort relationship, SSER). These two relationships differ in their nature and underlying mechanisms but are not clearly distinguished in field studies. To discriminate the effects of area (spatial extent) and sampling effort (SE) on species richness, several models explicitly involving both variables were proposed and tested against 13 datasets from marine micro-, meio- and macrobenthos. A combination of power SSER and piecewise power SAR terms was found to have the best fit. The effects of area and SE were both significant, but the former one was noticeably weaker. The SSERs were roughly linear in log-log space, whereas the SARs demonstrated scale-dependent behavior with a noticeable threshold (slope breakpoint). Species richness was almost area-independent below this threshold (the “small area effect”, SAE) but followed typical power-law SAR beyond the threshold. This effect was similar to the “small island effect” but occurred for arbitrarily delineated areas within continuous habitats. Parameters of the SAR curves depended on organism size. The upper limit of the SAE increased from microorganisms to meiofauna to macrofauna. Also, SAR curves for unicellular groups had significantly lower slopes. SAE is supposed to indicate a spatial range of statistical homogeneity in species composition. Its upper limit corresponds to the characteristic size of a local community (a single habitat occupied by a common species pool). Interpretations of SAR and SSER parameters in terms of α- and β-diversity are proposed. Both SAR and SSER slopes obtained from univariate regressions are overestimated. This upward bias depends on sampling design, decreasing for SAR but increasing for SSER with more unequally spaced samples. Both spatial extent and sampling effort should be taken into account to disentangle properly their effects on diversity.

Decadal-scale changes in abundance of non-scleractinian invertebrates on a Caribbean coral reef

The benthic community structure of the shallow reefs of St. John, US Virgin Islands, was studied from 1992 to 2007 to test the hypotheses that the abundances of non-scleractinian invertebrates have changed, and further, that the changes are associated with variation in the percentage cover of scleractinian coral and macroalgae. The study utilized photoquadrats (0.25 m 2) from fringing reefs (7–9 m depth) characterized by igneous boulders and low (< 5%) coral cover, and results from six sites were pooled to describe these reefs as a single habitat. Photoquadrats were analyzed biennially for the abundance of invertebrates, particularly those belonging to four well represented classes (Anthozoa, Demospongiae, Echinoidea, and Polychaeta), as well as the cover of scleractinians and macroalgae. Overall, the combined (multivariate) abundance of 30 invertebrate taxa changed over time, the combined (multivariate) abundance of the four invertebrate classes changed over time, and the individual (univariate) abundance of anthozoans, sponges, and echinoids changed over time. Throughout the study, coral cover remained < 5%, and while it varied significantly, it did not display a consistent trajectory of change; in contrast, the cover of macroalgae increased throughout the study. While it is unsurprising that the abundances of invertebrates changed over 15 y, notably they varied even though coral cover remained stable, in only a few cases were they related positively to macroalgal cover, and in most cases it was members of the suspension feeding guild that became more abundant. These outcomes suggest that: (1) benthic invertebrates on the shallow reefs of St. John may be more strongly influenced by regional (e.g., larva supply) than local (e.g., coral cover) conditions, (2) Caribbean reefs have changed more since the early 1990s than can be inferred from variation in cover of coral and macroalgae, and (3) suspension feeding invertebrates have become more common on shallow fringing reefs in at least one location.

Influence of Moisture and Food Supply on the Movement Dynamics of a Nonbreeding Migratory Bird (Parkesia noveboracensis) in a Seasonal Landscape

We radiotracked Northern Waterthrushes (Parkesia noveboracensis) in four habitats in Puerto Rico during two winters (i.e., January–April) in 2003 and 2004 to determine the ecological determinants of diurnal space use and overwinter sitepersistence in this species. The majority of birds (69%) were sedentary and used a contiguous area within a single habitat over the winter period. A smaller percentage (31%) initially used a contiguous area within a single habitat but then permanently moved from that area to another disjunct location (mean = 418 m). Most of these movements were out of the two habitats (dry forest and Black Mangrove) that became the driest from January to mid-March and into wetter mangrove areas. The primary determinants of movement probability were moisture and food availability on each bird's home range. Foraging areas of birds that eventually moved were drier and had lower food availability than areas used by site-persistent individuals. The sites that these itinerant birds moved to were wetter and had higher food availability, which suggests that individuals moved in response to changing resources. Our results (1) indicate that habitats used by this species differ in suitability and (2) support previous findings that turnover rates within a habitat could serve as an indicator of habitat quality. The ability to predict behavioral responses of individuals to habitat conditions that vary across space and time is essential for understanding individual and population responses to habitat loss and the effects of a changing climate in the New World tropics.

Accounting for the effects of biological variability and temporal autocorrelation in assessing the preservation of species abundance

Quantifying the effects of taphonomic processes on species abundances in time-averaged death assemblages (DAs) is pivotal for paleoecological inference. However, fidelity estimates based on conventional “live-dead” comparisons are fundamentally ambiguous: (1) data on living assemblages (LAs) are based on a very short period of sampling and thus do not account for biological variability in the LA, (2) LAs are sampled at the same time as the DA and thus do not necessarily reflect past LAs that contributed to the DA, (3) compositions of LAs and DAs can be autocorrelated owing to shared cohorts, and (4) fidelity estimates are cross-scale estimates because DAs are time-averaged and LAs are not. Some portion of raw (total) live-dead (LD) variation in species composition thus arises from incomplete sampling of LAs and from biological temporal variation among LAs (together = premortem component of LD variation), as contrasted withnewvariation created by interspecific variation in population turnover and preservation rates and by the time-averaging of skeletal input (together = postmortem component of LD variation). To tackle these problems, we introduce a modified test for homogeneity of multivariate dispersions (HMD) in order to (1) account for temporal autocorrelation in composition between LAs and DAs and (2) decompose total LD compositional variation into premortem and postmortem components, and we use simulations to evaluate the contribution of within-habitat time-averaging on the postmortem component. Applying this approach to 31 marine molluscan data sets, each consisting of spatial replicates of LAs and DAs in a single habitat, we find that total LD variation is driven largely by variation among LAs. However, genuinely postmortem processes have significant effects on composition in 25–65% of data sets (depending on the metric) when the effects of temporal autocorrelation are taken into account using HMD. Had we ignored the effects of autocorrelation, the effects of postmortem processes would have been negligible, inflating the similarity between LAs and DAs. Simulations show that within-habitat time-averaging does not increase total LD variation to a large degree—it increases total LD variation mainly via increasing species richness, and decreases total LD variation by reducing dispersion among DAs. The postmortem component of LD variation thus arises from differential turnover and preservation and multi-habitat time-averaging. Moreover, postmortem processes have less effect on the compositions of DAs in habitats characterized by high variability among LAs than they have on DAs in temporally stable habitats, a previously unrecognized first-order factor in estimating postmortem sources of compositional variation in DAs.

Sustainability without coexistence state in Durrett–Levin hawk–dove model

Models that explain the sustainability of an exploiter–victim ecosystem admit, generally, a coexistence state of both species in the well-mixed limit. Even if this state is unstable, the extinction-prone system may acquire stability on spatial domains where different patches oscillate incoherently around the coexistence state. New experiments, however, suggest that a spatially segregated system may be stable even in the absence of such a coexistence state. Here we revisit the hawk–dove (case 3) model of Durrett and Levin, which has been shown to support persistent population for system of interacting particles. It turns out that this model does not admit a (stable or unstable) coexistence state on a single habitat. We analyze the peculiar mechanism that leads to persistence in this case and the role of demographic stochasticity with and without self-interaction, using numerical simulations and exact solutions in the infinite diffusion limit.

Co-circulation of Emerging Tick-Borne Pathogens in Middle Germany

From May until October 2007, a total of 658 Ixodes ricinus ticks were collected off birds (189), rodents (273), and vegetation (196) in a certain area of Middle Germany and investigated for infection with Babesia spp., Anaplasma phagocytophilum, and Rickettsia spp. Overall, 13.1% (86/658) of the ticks were infected with at least one pathogen; co-infections occurred in 0.6% (4/658). Babesia spp. specific DNA was detected in 9.7% (64/658) of the ticks, 1.4% (9/658) were infected with A. phagocytophilum, and 2.6% (17/658) harbored rickettsiae. At least two different Rickettsia species were identified: Rickettsia monacensis and Rickettsia helvetica. Our study provides first interesting insights into the circulation and co-circulation of several emerging pathogens not only in ticks parasitizing birds and small mammals as potential reservoirs but also in questing ticks in a single natural habitat.

Relevance of multiple spatial scales in habitat models: A case study with amphibians and grasshoppers

Habitat models for animal species are important tools in conservation planning. We assessed the need to consider several scales in a case study for three amphibian and two grasshopper species in the post-mining landscapes near Leipzig (Germany). The two species groups were selected because habitat analyses for grasshoppers are usually conducted on one scale only whereas amphibians are thought to depend on more than one spatial scale. First, we analysed how the preference to single habitat variables changed across nested scales. Most environmental variables were only significant for a habitat model on one or two scales, with the smallest scale being particularly important. On larger scales, other variables became significant, which cannot be recognized on lower scales. Similar preferences across scales occurred in only 13 out of 79 cases and in 3 out of 79 cases the preference and avoidance for the same variable were even reversed among scales. Second, we developed habitat models by using a logistic regression on every scale and for all combinations of scales and analysed how the quality of habitat models changed with the scales considered. To achieve a sufficient accuracy of the habitat models with a minimum number of variables, at least two scales were required for all species except for Bufo viridis, for which a single scale, the microscale, was sufficient. Only for the European tree frog ( Hyla arborea), at least three scales were required. The results indicate that the quality of habitat models increases with the number of surveyed variables and with the number of scales, but costs increase too. Searching for simplifications in multi-scaled habitat models, we suggest that 2 or 3 scales should be a suitable trade-off, when attempting to define a suitable microscale.

Parallel habitat specialization within the wolf spider genusHognafrom the Galápagos

Within most island archipelagos, such as the Galápagos, similar ecological gradients are found on geographically isolated islands. Species radiations in response to these ecological gradients may follow different scenarios being (i) a single habitat specialization event followed by secondary colonization of each ecotype on the different islands or (ii) repeated and parallel habitat specialization on each island separately. This latter scenario has been considered less likely as gene flow might hamper such ecotypic differentiation. At least for the Galápagos, the extent to which this process is involved in species radiations remains yet poorly understood. Within the wolf spider genus Hogna, seven species are described that can be divided into three different ecotypes based on general morphology and habitat preference i.e. species that inhabit the pampa vegetation in the highlands, species that occur in coastal dry habitats and one generalist species. Comparison of the species phylogeny based on one mitochondrial (COI) and one nuclear (28S) gene fragment convincingly demonstrates that 'pampa' and 'coastal dry' species evolved in parallel on the islands Santa Cruz and San Cristóbal. Despite the observation that allozymes analysis indicated that each species forms a distinct genetic cluster, phylogenetic divergence within these species complexes was very low and paraphyletic and most likely due to hybridization rather than incomplete lineage sorting, as demonstrated for the Santa Cruz species complex. This suggests that within-island speciation occurred under low levels of gene flow. Species phylogeny in general did not follow the progression of island emergence as a molecular clock analysis suggested that island endemic species may have diverged after as well as before the emergence of the islands. This represents the first clear example of parallel and within-island speciation because of habitat specialization on the Galápagos and that such divergence most likely occurred under historic gene flow.

Coexistence of Pathogens in Host-Seeking and Feeding Ticks within a Single Natural Habitat in Central Germany

The importance of established and emerging tick-borne pathogens in Central and Northern Europe is steadily increasing. In 2007, we collected Ixodes ricinus ticks feeding on birds (n = 211) and rodents (n = 273), as well as host-seeking stages (n = 196), in a habitat in central Germany. In order to find out more about their natural transmission cycles, the ticks were tested for the presence of Lyme disease borreliae, Anaplasma phagocytophilum, spotted fever group (SFG) rickettsiae, Francisella tularensis, and babesiae. Altogether, 20.1% of the 680 ticks examined carried at least one pathogen. Bird-feeding ticks were more frequently infected with Borrelia spp. (15.2%) and A. phagocytophilum (3.2%) than rodent-feeding ticks (2.6%; 1.1%) or questing ticks (5.1%; 0%). Babesia spp. showed higher prevalence rates in ticks parasitizing birds (13.2%) and host-seeking ticks (10.7%), whereas ticks from small mammals were less frequently infected (6.6%). SFG rickettsiae and F. tularensis were also found in ticks collected off birds (2.1%; 1.2%), rodents (1.8%; 1.5%), and vegetation (4.1%; 1.6%). Various combinations of coinfections occurred in 10.9% of all positive ticks, indicating interaction of transmission cycles. Our results suggest that birds not only are important reservoirs for several pathogens but also act as vehicles for infected ticks and might therefore play a key role in the dispersal of tick-borne diseases.

Broad-Scale Relations between Conservation Reserve Program and Grassland Birds: Do Cover Type, Configuration and Contract Age Matter?~!2010-03-03~!2010-06-20~!2010-08-07~!

The Conservation Reserve Program (CRP) is a voluntary cropland set-aside program where environmentally- sensitive cropland is retired to a conservation practice. Grassland birds should benefit because most CRP is grass habitat and because amount of land in CRP is highest in agriculture-dominated areas of the United States where grassland habitat has been most impacted. We used the Breeding Bird Survey and Common Land Unit (CLU) data (spatially-explicit data of farm field boundaries and land cover) to identify relations between types and configurations of CRP and grassland bird abundance in 3 Midwestern states. All 13 species we studied were related to at least one aspect of CRP habitat - specific conservation practices (e.g., native vs. exotic grass), CRP habitat configuration, or habitat age. Treating all types of CRP as a single habitat type would have obscured bird-CRP relations. Based on our results, creating a mosaic of large and small set-aside patches could benefit both area-sensitive and edge-associated grassland birds. Additionally, northern bobwhite and other birds that use early successional grasslands would benefit from periodic disturbances. CRP, agri- environment schemes, and other government-sponsored set-aside programs may be most successful when administered as part of a targeted, regional conservation plan.

Red king crab ( Paralithodes camtschaticus) early post-settlement habitat choice: Structure, food, and ontogeny

Little is known about nursery habitat function for red king crab ( Paralithodes camtschaticus), a commercially important species that associates with complex benthic habitats from settlement through the first two years of life. During settlement, the red king crab actively seeks complex benthic habitats, with high availability of vertical structure and crevice space. Habitat choice for early juvenile red king crab may be driven by habitat complexity, or a function of several potential mechanisms, including foraging requirements, and shifting ontogeny. We established habitat preference and foraging behavior for two size classes of age-0 red king crab (small 2–4 mm, and large 7.5–9 mm carapace length) with laboratory experiments using habitat treatments composed of individual complex substrates that were living, biogenic substrates, including structural invertebrates, bryozoans and hydroids, and macroalgae in branched and blade forms. Non-living structural mimics of the biogenic substrates were presented to crabs as clean and fouled mimic treatments. We quantified the proportion of crab associations and foraging activity with single habitat treatments within a 24 h period. Substrates that were statistically attractive to small crabs were paired to test small crab foraging behavior. A variety of substrates were statistically attractive to red king crab. Small crabs associated with complex biogenic habitats and fouled mimics (group mean ± SE 64% ± 4%) more often than clean mimics (29% ± 4%), and preferred to forage on the structural invertebrates (foraging frequency 81%) when presented with paired biogenic and fouled mimic substrates. Large crabs associated with habitats composed of structural invertebrates (group mean ± SE 78% ± 2%) statistically more often than macroalgae and fouled and clean mimics (32% ± 5%). Strong attraction to structural invertebrates by early juvenile red king crab is likely driven by foraging opportunities. Our experiments demonstrate that biological habitat features may be functionally more important to early juvenile red king crab than complex physical structure alone. Habitats formed by structural invertebrates, in particular, may enhance growth and survival of early post-settlement stage red king crab in excess of other highly structured habitats, including macroalgae and complex physical substrates.