Adult Habitat Research Articles

Geographic coupling of juvenile and adult habitat shapes spatial population dynamics of a coral reef fish

Marine spatial population dynamics are often addressed with a focus on larval dispersal, without taking into account movement behavior of individuals in later life stages. Processes occurring during demersal life stages may also drive spatial population dynamics if habitat quality is perceived differently by animals belonging to different life stages. In this study, we used a dual approach to understand how stage-structured habitat use and dispersal ability of adults shape the population of a marine fish species. Our study area and focal species provided us with the unique opportunity to study a closed island population. A spatial simulation model was used to estimate dispersal distances along a coral reef that surrounds the island, while contributions of different nursery bays were determined based on otolith stable isotope signatures of adult reef fish. The model showed that adult dispersal away from reef areas near nursery bays is limited. The results further show that different bays contributed unequally to the adult population on the coral reef, with productivity of juveniles in bay nursery habitat determining the degree of mixing among local populations on the reef and with one highly productive area contributing most to the island's reef fish population. The contribution of the coral reef as a nursery habitat was minimal, even though it had a much larger surface area. These findings indicate that the geographic distribution of nursery areas and their productivity are important drivers for the spatial distribution patterns of adults on coral reefs. We suggest that limited dispersal of adults on reefs can lead to a source-sink structure in the adult stage, where reefs close to nurseries replenish more isolated reef areas. Understanding these spatial population dynamics of the demersal phase of marine animals is of major importance for the design and placement of marine reserves, as nursery areas contribute differently to maintain adult populations.

Field test of the behavioral regulation of larval transport

The maintenance of marine populations depends on the completion of larval migrations between adult and larval habitats, but the ability of microscopic larvae to regulate their movements in such a dynamic environment has been debated. Using a comparative hypothesis testing approach and intensive hourly sampling throughout the water column, we determined the ability of larvae of 6 species with different swimming abilities (2 gastropods, 2 crabs, 2 fishes) to overcome strong tidal mixing during spring tides and regulate their vertical, and hence, horizontal position, in opposing depth-stratified currents in the upper Hudson River estuary, USA. The vertical distributions of nonmotile eggs and swimming larvae generally differed, suggesting that larvae regulated depth. Eggs were passively mixed by tidal currents, but larvae typically aggre- gated in stratified portions of the water column, which fostered retention in the upper estuary. However, the capacity to regulate depth depended on swimming ability and the degree of mixing. In a predominantly mixed tidal environment upstream, mixing overcame most larvae when current velocities were maximal during mid-ebb or mid-flood tides; tidal vertical migrations were not evident for any species, and diel vertical migrations were apparent for only 1 species. In a partially stratified water column downstream, diel vertical migrations were apparent for larvae of 3 of 4 invertebrate species, and tidal vertical migrations were apparent for the 2 fish species. The presence of all larval stages showed that all species regulated depth sufficiently well to remain in the upper estuary. Regardless of swimming ability, larvae were retained in the estuary by occur- ring near the level of no net motion, even without completing tidal vertical migrations. Continuous profiling of larvae and hydrodynamics is necessary to reveal the ability of larvae to regulate depth in tidal mixing and recruit to adult populations.

Summer Habitat Use of Large Adult Striped Bass and Habitat Availability in Lake Martin, Alabama

AbstractTo identify the summer habitat use by Gulf strain Striped Bass Morone saxatilis in Lake Martin, Alabama, 36 fish greater than 4 kg were tracked weekly from June through September in 2009 and 2010. Temperature and dissolved oxygen profiles were collected biweekly from July to October each year and were incorporated into a hypsographic curve to estimate summertime volumes of Striped Bass habitat. Striped Bass moved downstream in the reservoir and deeper in the water column as the summer progressed in both years. Across all temperatures and dissolved oxygen concentrations (DOCs) measured, fish generally selected cooler temperatures when DOCs were greater than 3.1 mg/L, but below that level, fish selected warmer temperatures. By early July each year, quality Striped Bass habitat (≤21.0°C and ≥3.2 mg/L DOC) comprised 40–50% of the total habitat available in Lake Martin. However, in 2009 all quality habitat was gone from the reservoir by August 1, and total habitat (≤25.0°C and ≥1.6 mg/L DOC) rapidly decreased until there was no suitable habitat found in Lake Martin by mid‐September. The quantity of quality and total habitat declined more rapidly in 2009 than in 2010; although quality habitat was eliminated from the reservoir by the end of August 2010, total habitat persisted throughout the summer. In both years, habitat availability increased when reservoir destratification began. Analysis of historical data indicated that quality habitat was found in the lower portion of the reservoir during the latter half of August in only 6 of 15 years; total Striped Bass habitat was available in all but 1 year. The amount of water flowing through the system during the spring and summer was a key determinant of Striped Bass habitat availability by late summer.Received September 26, 2012; accepted May 15, 2013

Effects of an Invasive Plant on Population Dynamics in Toads

When populations decline in response to unfavorable environmental change, the dynamics of their population growth shift. In populations that normally exhibit high levels of variation in recruitment and abundance, as do many amphibians, declines may be difficult to identify from natural fluctuations in abundance. However, the onset of declines may be evident from changes in population growth rate in sufficiently long time series of population data. With data from 23 years of study of a population of Fowler's toad (Anaxyrus [ = Bufo] fowleri) at Long Point, Ontario (1989-2011), we sought to identify such a shift in dynamics. We tested for trends in abundance to detect a change point in population dynamics and then tested among competing population models to identify associated intrinsic and extrinsic factors. The most informative models of population growth included terms for toad abundance and the extent of an invasive marsh plant, the common reed (Phragmites australis), throughout the toads' marshland breeding areas. Our results showed density-dependent growth in the toad population from 1989 through 2002. After 2002, however, we found progressive population decline in the toads associated with the spread of common reeds and consequent loss of toad breeding habitat. This resulted in reduced recruitment and population growth despite the lack of significant loss of adult habitat. Our results underscore the value of using long-term time series to identify shifts in population dynamics coincident with the advent of population decline.

Ontogenetic shift in stress tolerance thresholds of Mytilus trossulus: effects of desiccation and heat on juvenile mortality

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 481:147-159 (2013) - DOI: https://doi.org/10.3354/meps10221 Ontogenetic shift in stress tolerance thresholds of Mytilus trossulus: effects of desiccation and heat on juvenile mortality Brittany T. Jenewein1, Louis A. Gosselin1,2,* 1Department of Biological Sciences, Thompson Rivers University, 900 McGill Road, Kamloops British Columbia V2C 0C8, Canada 2Department of Biology, University of Victoria, Victoria British Columbia V8W 3N5, Canada *Corresponding author. Email: lgosselin@tru.ca ABSTRACT: We examined the sensitivity of newly settled Mytilus trossulus to heat and desiccation, as well as the ontogeny of sensitivity through the early benthic phase. Laboratory experiments were conducted to determine the sensitivity of mussels to the full range of temperatures and desiccation levels experienced in the field. Mussels of 1 to 2 mm shell length (SL) experienced a threshold of heat tolerance at 34°C and a threshold of desiccation tolerance at vapour pressure deficit levels of 1.01 kPa. Extended periods of temperatures reaching or exceeding lethal levels for newly settled M. trossulus occurred relatively rarely in Barkley Sound, British Columbia, Canada, whereas lethal levels of desiccation occurred often during the recruitment season and were usually sustained for several hours. Desiccation, therefore, appears to be a substantially greater threat to recently settled M. trossulus than heat. A final laboratory experiment characterized the changes in sensitivity to desiccation that occur as mussels increase in size. Mussels became highly tolerant to desiccation when they reached a size of 2 to 3 mm SL. This size closely corresponds to the size at which juvenile M. trossulus relocate from protective filamentous algal habitat to adult habitat, suggesting ontogenetic shifts in habitat use by juvenile M. trossulus are a response to changing sensitivity to desiccation. If so, the future survival of newly settled mussels, and thus possibly the local persistence of mussel populations, may depend upon the persistence of protective algal microhabitats under changing climate conditions. KEY WORDS: Early post-settlement mortality · Mortality factors · Physiological stress · Weather · Settlement · Recruitment · Population regulation · Climate change Full text in pdf format PreviousNextCite this article as: Jenewein BT, Gosselin LA (2013) Ontogenetic shift in stress tolerance thresholds of Mytilus trossulus: effects of desiccation and heat on juvenile mortality. Mar Ecol Prog Ser 481:147-159. https://doi.org/10.3354/meps10221 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 481. Online publication date: May 07, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

HYDRAULIC GEOMETRY AND LONGITUDINAL PATTERNS OF HABITAT QUANTITY AND QUALITY FOR RAINBOW TROUT (Oncorhynchus mykiss)

ABSTRACTWe developed predictions of habitat quantity and quality for three life stages of rainbow trout, Oncorhynchus mykiss, across a range of stream sizes characterized by mean annual discharge of 1 to 50 m3 s−1. The physical habitat template was created by nesting a reach‐scale two‐dimensional hydrodynamic model (River2D) within a downstream hydraulic geometry system using published coefficients for low‐gradient and high‐gradient watersheds. This provided both longitudinal and transverse estimates of depth and velocity profiles that, when combined with habitat suitability curves for the life stages, resulted in predictions of habitat quantity (weighted usable area) and habitat quality (the proportion of the stream profile that provided useable habitat) for rainbow trout along the stream continuum. Habitat quantity increased asymptotically for all life history stages but increased more rapidly in the low‐gradient watershed. Habitat quality decreased non‐linearly for young‐of‐the‐year and peaked at intermediate stream sizes for juveniles in both low‐gradient and high‐gradient watersheds. Adult habitat quality peaked in the high‐gradient watershed but increased asymptotically in the low‐gradient watershed, presumably due to lower mean velocities at larger stream sizes. Incorporation of transverse variation in depth and velocity in our physical habitat template provides a more realistic representation of habitat quantity and quality than do earlier assessments based on simple modal estimates of depth and velocity. Copyright © 2013 John Wiley & Sons, Ltd.

Ecological trade-offs in seascape ecology: bay scallop survival and growth across a seagrass seascape

In marine systems, seagrass meadows, which serve as essential nursery and adult habitat for numerous species, experience fragmentation through both human activity and environmental processes. Results from studies involving seagrass patch size and edge effects on associated fauna have shown that patchy seagrass habitats can be either beneficial or detrimental. One reason for the variable results might be the existence of ecological trade-offs for species that associate with seagrass habitats. Bay scallops, Argopecten irradians, are useful model organisms for studying the response of a semi-mobile bivalve to changes in seagrass seascapes—they exhibit a strong habitat association and seagrass offers a predation refuge at a cost of reduced growth. This study investigated the potential ecological survival–growth trade-off for bay scallops living within a seagrass seascape. Scallop growth was consistently fastest in bare sand and slowest at patch centers, and survival showed the opposite trend. Scallops in patch edges displayed intermediate growth and survival. Using models for minimizing mortality (μ) to foraging (f) ratios, the data suggests seagrass edge habitat offered similar value to patch centers. Further, investigations of core-area index suggest that small, complex patches might offer scallops a balance between predation risk and maximized growth. Taken in sum, these results suggest that edge habitats may benefit organisms like bay scallops by maximizing risk versus reward and maximizing edge habitat.

Turbulent shear spurs settlement in larval sea urchins.

Marine invertebrates commonly produce larvae that disperse in ocean waters before settling into adult shoreline habitat. Chemical and other seafloor-associated cues often facilitate this latter transition. However, the range of effectiveness of such cues is limited to small spatial scales, creating challenges for larvae in finding suitable sites at which to settle, especially given that they may be carried many kilometers by currents during their planktonic phase. One possible solution is for larvae to use additional, broader-scale environmental signposts to first narrow their search to the general vicinity of a candidate settlement location. Here we demonstrate strong effects of just such a habitat-scale cue, one with the potential to signal larvae that they have arrived in appropriate coastal areas. Larvae of the purple sea urchin (Strongylocentrotus purpuratus) exhibit dramatic enhancement in settlement following stimulation by turbulent shear typical of wave-swept shores where adults of this species live. This response manifests in an unprecedented fashion relative to previously identified cues. Turbulent shear does not boost settlement by itself. Instead, it drives a marked developmental acceleration that causes "precompetent" larvae refractory to chemical settlement inducers to immediately become "competent" and thereby reactive to such inducers. These findings reveal an unrecognized ability of larval invertebrates to shift the trajectory of a major life history event in response to fluid-dynamic attributes of a target environment. Such an ability may improve performance and survival in marine organisms by encouraging completion of their life cycle in advantageous locations.

Morphological character changes through decapodid-stage larva and juveniles in the ghost shrimp Nihonotrypaea harmandi from western Kyushu, Japan: Clues for inferring pre- and post-settlement states and processes

Some decapod crustaceans release larvae from estuarine or coastal shores to coastal oceans. Decapodids (last-stage larvae) return home, settle, and metamorphose into juveniles I, which go through further instars. Several morphological characters degenerate or develop in response to lifestyle transitions. Using a burrow-dwelling callianassid shrimp, Nihonotrypaea harmandi, inhabiting an intertidal sandflat in a coastal boundary layer adjacent to coastal ocean, this study described morphological changes and drew inferences about states and processes in its early life history. Decapodid and juveniles were differentiated by linea thalassinica on carapace. In the laboratory, the decapodid stage lasted 3–6d. Given choice between sandy sediments from coastal ocean bed and adult habitat, decapodids exhibited no preference, suggesting broad receptiveness. The shortest durations of the juvenile-I, -II, and -III were estimated at 6d each. Starved decapodids normally metamorphosed into juveniles I, showing secondary lecithotrophy. The non-feeding state could be extended through the juvenile I (and possibly juvenile II), where the mean total lengths of shrimps reared in groups with food (diatoms) remained about 4.6mm. Post-settlement decapodids reared individually resumed feeding. The rostrum lengths in decapodids were ≥0.36mm on the initial two dates (Days 0 and 1), after which the mean values rapidly reduced to 0.30–0.36mm on Day 2 and below 0.30mm thereafter. The pereiopod exopods disappeared through the decapodid stage from four pairs to almost zero by Day 4. In the coastal ocean, no juveniles occurred, and almost all decapodids had rostrum lengths ≥0.30mm and 3 or 4 pereiopod exopods, suggesting their pre-settlement state. Of the smallest shrimps collected on the sandflat for their subsequent rearing there, 74% were estimated to be Day-0 or -1 decapodids based on their rostrum lengths. This and the laboratory experimental results suggest (1) the acquisition of competence for settlement by newly-metamorphosed decapodids while in the coastal ocean, which was nevertheless realized there and (2) their rapid transport by flood tidal currents from coastal ocean to sandflat. The newly-settled decapodids grew steadily at 0.2mmd−1 in total length. The reared juveniles reached the smallest adult size in 80d. The uropod expod changed from elliptical to sub-circular in shape markedly around the termination of the juvenile II or III, suggesting the acquisition of ventilating function for benthic life. Overall, the post-settlement shrimps can be staged by total-length ranges as 4–5.5mm for decapodids, 5.5–10mm for juveniles, and 10–20mm for sub-adults.

Adult activity and oviposition of corn rootworms, Diabrotica spp. (Coleoptera: Chrysomelidae), in Miscanthus, corn and switchgrass

The ability of the biomass crop Miscanthus (Miscanthus × giganteus Greef and Deuter ex Hodkinson and Renvoize) to support larval development for both United States and European populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, suggests an avenue for interactions with corn (Zea mays L.). To provide context to survival of D. v. virgifera on Miscanthus, adult activity and oviposition of Diabrotica spp. were monitored in central Illinois in 2010–2011 in Miscanthus, corn and switchgrass (Panicum virgatum L.). For D. v. virgifera, vial traps within corn plots captured 3–10 times as many adults as in Miscanthus or switchgrass, while soil samples showed females laid approximately 10 times as many eggs in corn as in the perennial grasses. Adult southern corn rootworms, Diabrotica undecimpunctata howardi Barber, were the most abundant species in 2010 and clearly preferred switchgrass as an adult habitat, with vial traps in switchgrass capturing 5–10 times as many D. u. howardi as those in corn or Miscanthus. Based on the small production areas for Miscanthus and switchgrass (and low use of both by D. v. virgifera), it seems likely that there are no current impacts of these perennial grasses on pest status of Diabrotica spp. in corn or other crops. However, adaptations by Diabrotica spp. to pest management practices suggest they could be a source for interactions between biomass and food or feed crops. Early-season soil samples did not recover eggs of D. u. howardi, but their use of switchgrass as an adult habitat suggests additional research in areas where switchgrass may be grown near peanuts, alfalfa or other hosts may be needed. Also, investigation of other candidate bioenergy crops known to support Diabrotica spp. larval development is needed to better understand the possible effects of a changing agricultural landscape on corn rootworms.

What Drives Ontogenetic Niche Shifts of Fishes in Coral Reef Ecosystems?

Ontogenetic niche shifts are taxonomically and ecologically widespread across the globe. Consequently, identifying the ecological mechanics that promote these shifts at diverse scales is central to an improved understanding of ecosystems generally. We evaluated multiple potential drivers of ontogenetic niche shifts (predation, growth, maturation, diet shifts, and food availability) for three fish species between connected coral reef and nearshore habitats. In all cases, neither diet compositional change nor sexual maturity functioned as apparent triggers for emigration from juvenile to adult habitats. Rather, the fitness advantages conferred on reef inhabitants (that is, enhanced growth rates) were primarily related to high prey availability on reefs. However, there exists a clear trade-off to this benefit as survival rates for small fishes were significantly reduced on reefs, thereby revealing the potential value of (and rationale behind high juvenile abundances in) nearshore habitat as predation refugia. We ultimately conclude that predation risk functions as the primary early life stage inhibitor of ontogenetic niche shifts towards more profitable adult habitats in these systems. Furthermore, this study provides a case study for how complex, meta-dynamic populations and ecosystems might be better understood through the elucidation of simple ecological trade-offs.

Settlement and recruitment of the barnacleBalanus amphitritefrom a tropical environment influenced by monsoons

Studies on the settlement and the subsequent recruitment of intertidal organisms are crucial steps in understanding their population structure in a particular bioregion. However, studying the recruitment of intertidal organisms such as barnacles, with two-phase life cycle, and understanding the determinants of recruitment is a complex problem. Many processes which operate during the pelagic pre-settlement phase and benthic post-settlement phase at different spatial and temporal scales can determine the fate of barnacle populations. In this study, observations were carried out on settlement and recruitment of the intertidal barnacleBalanus amphitritefrom a tropical environment influenced by monsoons at spatial and temporal scales. Settlement and recruitment both showed significant temporal variations. In general, settlement and recruitment was lower during the monsoon season except during monsoon breaks. Consistency in settlement and recruitment was mostly observed during the pre-monsoon season, and it coincided with peaks in larval abundance observed during the same season. In general, settlement remained more or less similar on different types of substrata, whereas recruitment differed significantly. Temporal variations observed in settlement and recruitment of barnacles could be due to the influence of monsoons in this region, which leads to seasonal fluctuations in physical factors such as local hydrodynamics, that influence the retention and dispersal of larvae in the adult habitats, and could also be due to variations in the availability of food for the larvae and the settled populations.

Effects of hunter access and habitat security on elk habitat selection in landscapes with a public and private land matrix

AbstractTraditional elk habitat management on public land has focused on providing security habitat for bull elk during the hunting season to provide for both adequate hunter opportunity and bull survival. This paradigm has given less consideration to adult female elk habitat use, patterns of adjacent land ownership, and hunter access. This paradigm also was developed when elk population sizes were much smaller in many areas. In many Rocky Mountain states, the focus of elk population management has recently shifted to reducing or maintaining elk population sizes, necessitating a better understanding of the implications of security habitat management, as well as patterns of adjacent land ownership and hunter access, on adult female elk. We addressed this need by testing the hypotheses that during the hunting season: 1) adult female elk selection for areas prohibiting or limiting hunter access is stronger than elk selection for publicly owned and managed elk security habitat, 2) these effects occur during the archery hunting period and intensify during the rifle hunting period, and 3) the effects of hunter access on selection are consistent among herds that occupy landscapes characterized by a matrix of public and private lands. We used global position system locations collected from 82 females in 2 different Greater Yellowstone Ecosystem (GYE) elk herds to evaluate effects of hunter access, security habitat as defined by the Hillis paradigm, and other landscape attributes on adult female elk resource selection during the pre‐hunting, archery, rifle, and post‐hunting periods. We found that female elk selection for areas restricting public hunting access was stronger than selection for security habitat in both study areas, and that the density of roads open to motorized use was the strongest predictor of elk distribution. Increases in selection for areas that restricted hunting access occurred during the rifle hunting period, and we did not find consistent evidence these movements were triggered by the archery hunting period. Our results provide evidence that in landscapes characterized by a matrix of public and privately owned lands, traditional concepts of elk security habitat need to be expanded to also include areas that restrict hunter access to plan for elk population management that is regulated through adult female harvest. Future efforts should investigate whether elk use of areas that restrict hunter access are flexible behavioral responses to hunting risk, or if these behaviors are passed from generation to generation such that a learned pattern of private land use becomes the normal movement pattern rather than a short‐term behavioral response. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

The saproxylic hoverflies (Diptera: Syrphidae) of Serbia

The revision of the saproxylic hoverflies collected in Serbia from 1950 to 2010 has revealed a total of 56 species, of which Sphiximorpha subsessilis (Illiger in Rossi) is new to the Balkan Peninsula and Arctophila superbiens (Muller), Blera fallax (Linnaeus), Brachyopa panzeri Goffe, Brachyopa testacea (Fallén), Brachyopa vittata Zetterstedt and Chalcosyrphus piger (Fabricius) are new to Serbia. According to “Syrph the Net, the database of European Syrphidae”, 16 of the 56 species are threatened with extinction in Europe, while 6 species are “strictly protected” and 13 are “protected” under Serbian legislation. Distribution maps for each species, as well as new data on adult habitats, are provided. The conservation status of the saproxylic hoverflies of Serbia is discussed. The present study attempts to provide a basis for the conservation of the saproxylic hoverflies of this Balkan country.

Age and growth of European barbelBarbus barbus(Cyprinidae) in the small, mesotrophic River Lee and relative to other populations in England

Suspected of being in decline, the European barbel Barbus barbus population of the River Lee, a heavily-modified river in South East England, has been the subject of investigations to identify factors associated with perceived population decreases. Population surveys between 1995 and 1999 captured a total of 912 individuals, and standard length (SL) frequency analyses between years suggested that the population decline was not related to juvenile recruitment but rather to a recruitment bottleneck in fish 300–340 mm SL. This bottleneck probably results from insufficient available habitat suitable to this size class. Of the sampled fish, scales were removed from 764 and were used in a scale ageing exercise among three researchers. Analyses of their independent age estimates revealed variable interpretations, which arose from uncertainties relating to the difficulty of analysing scale patterns from relatively large, slow-growing fish. Nevertheless, error was within published acceptable margins, and age estimates revealed B. barbus in the river to age 10 years, lower than in many UK rivers. The SL-at-age growth curve was characterised by very fast growth in the initial years of life. Thus, the causal factors in the decline of this B. barbus population appear to have been in the adult life-stage habitat and were likely related to the loss of longitudinal connectivity, mainly due to the presence of water retention structures. River and aquatic ecosystem remediation strategies should therefore focus on enhancing longitudinal connectivity in conjunction with the ongoing improvement of water quality and ecosystem integrity.

Habitat-specific shaping of proliferation and neuronal differentiation in adult hippocampal neurogenesis of wild rodents

Daily life of wild mammals is characterized by a multitude of attractive and aversive stimuli. The hippocampus processes complex polymodal information associated with such stimuli and mediates adequate behavioral responses. How newly generated hippocampal neurons in wild animals contribute to hippocampal function is still a subject of debate. Here, we test the relationship between adult hippocampal neurogenesis (AHN) and habitat types. To this end, we compare wild Muridae species of southern Africa [Namaqua rock mouse (Micaelamys namaquensis), red veld rat (Aethomys chrysophilus), highveld gerbil (Tatera brantsii), and spiny mouse (Acomys spinosissimus)] with data from wild European Muridae [long-tailed wood mice (Apodemus sylvaticus), pygmy field mice (Apodemus microps), yellow-necked wood mice (Apodemus flavicollis), and house mice (Mus musculus domesticus)] from previous studies. The pattern of neurogenesis, expressed in normalized numbers of Ki67- and Doublecortin(DCX)-positive cells to total granule cells (GCs), is similar for the species from a southern African habitat. However, we found low proliferation, but high neuronal differentiation in rodents from the southern African habitat compared to rodents from the European environment. Within the African rodents, we observe additional regulatory and morphological traits in the hippocampus. Namaqua rock mice with previous pregnancies showed lower AHN compared to males and nulliparous females. The phylogenetically closely related species (Namaqua rock mouse and red veld rat) show a CA4, which is not usually observed in murine rodents. The specific features of the southern environment that may be associated with the high number of young neurons in African rodents still remain to be elucidated. This study provides the first evidence that a habitat can shape adult neurogenesis in rodents across phylogenetic groups.

Depth-Variable Settlement Patterns and Predation Influence on Newly Settled Reef Fishes (Haemulon spp., Haemulidae)

During early demersal ontogeny, many marine fishes display complex habitat-use patterns. Grunts of the speciose genus Haemulon are among the most abundant fishes on western North Atlantic coral reefs, with most species settling to shallow habitats (≤12 m). To gain understanding into cross-shelf distributional patterns exhibited by newly settled stages of grunts (<2 cm total length), we examined: 1) depth-specific distributions of congeners at settlement among sites at 8 m, 12 m, and 21 m, and 2) depth-variable predation pressure on newly settled individuals (species pooled). Of the six species identified from collections of newly settled specimens (n = 2125), Haemulon aurolineatum (tomtate), H. flavolineatum (French grunt), and H. striatum (striped grunt) comprised 98% of the total abundance; with the first two species present at all sites. Prevalence of H. aurolineatum and H. flavolineatum decreased substantially from the 8-m site to the two deeper sites. In contrast, H. striatum was absent from the 8-m site and exhibited its highest frequency at the 21-m site. Comparison of newly settled grunt delta density for all species on caged (predator exclusion) and control artificial reefs at the shallowest site (8-m) revealed no difference, while the 12-m and 21-m sites exhibited significantly greater delta densities on the caged treatment. This result, along with significantly higher abundances of co-occurring piscivorous fishes at the deeper sites, indicated lower predation pressure at the 8-m site. This study suggests habitat-use patterns of newly settled stages of some coral reef fishes that undergo ontogenetic shifts are a function of depth-variable predation pressure while, for at least one deeper-water species, proximity to adult habitat appears to be an important factor affecting settlement distribution.

Habitat‐related patterns in phenotypic variation in a New Zealand freshwater generalist fish, and comparisons with a closely related specialist

Summary1. Within‐species phenotypic variation is hugely variable and may play a role in determining the range of habitats a species can exploit. Our study addressed two main questions: 1. does phenotypic variation allow some species (i.e. habitat‐generalists) to use heterogeneous habitats and 2. are habitat‐generalists more variable than species occupying relatively homogeneous environments (i.e. habitat‐specialists)?2. We examined the morphology of the common bully (Gobiomorphus cotidianus), a habitat‐generalist eleotrid fish found in lakes and rivers throughout New Zealand. We also compared the level of morphological variability in common bullies with that in the closely related redfin bully (Gobiomorphus huttoni), a habitat‐specialist of moderate‐ and fast‐flowing rivers.3. Common and redfin bullies were collected from the South Island of New Zealand. A series of body and fin measurements were made, and cephalic dorsal head pores of the mechanosensory lateral‐line system were counted. The pores and associated canal neuromasts are important for prey detection and predator avoidance in other species, particularly, in turbulent conditions where the effectiveness of superficial neuromasts may be compromised.4. The common bully had more dorsal head pores in fish from rivers than in those from lakes. This pattern was apparent only in adults, suggesting that selective pressures associated with adult habitat, be it rivers or lakes, are responsible.5. As expected, there was greater phenotypic variability in the generalist common bully than in the specialist redfin bully, particularly with regard to the sensory pores, suggesting their importance for survival in turbulence.6. We identified habitat‐related patterns in phenotypic variability in a generalist species and demonstrated a link between phenotypic variability and habitat breadth. Variation in the common bully may explain its ability to occupy a range of habitats.

Restoration of a wild grey partridge shoot: a major development in the Sussex study, UK

The scientific basis of wild grey partridge management has been known for a generation. This includes controlling nest predators, providing nesting cover, having sufficient insect food for chicks and appropriate rates of shooting. More recently, measures such as providing food for adult birds and habitats for protection from birds of prey have also been considered important. Habitat provision can be expensive, but in the UK costs can be partially recovered through governmental agri–environment schemes. The landowner still needs to pay for the essential gamekeeper. Since 2003/04, one part of the Game &amp; Wildlife Conservation Trust’s (GWCT) Sussex Study area has put these principles of environmental management into practice with the aim of restoring a wild grey partridge shoot to this part of Southern England. Results have been impressive, with the spring pair density increasing from 0.3 pairs/100 ha in 2003 to nearly 20 pairs/100 ha in 2010 on an area of just over 10 km2. Over the past two years a wild grey partridge shoot has taken place, and the landowner and his team have gained national recognition for their conservation work.

Characterizing the potential habitat of European anchovy Engraulis encrasicolus in the Mediterranean Sea, at different life stages

AbstractIdentification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.