Population‐dependent acclimatization capacity of thermal tolerance in larvae of the rocky‐shore barnacle Pollicipes elegans

As environmental temperatures increase and become more seasonally variable, the ability of individuals to plastically alter their physiological responses to temperature (=acclimatize) may affect the potential for species persistence. Among marine organisms, the larval stage is often the most physiologically sensitive; larvae are also often the main dispersal stage in the life history. However, studies that address the acclimatization of marine larvae are rare. We investigated whether larvae of the gooseneck barnacle Pollicipes elegans from two temperate populations, one from the Northern Hemisphere (Mexico) and one from the Southern Hemisphere (Peru), show patterns of seasonal acclimatization to temperature. We compared the effects of temperature on swimming activity, oxygen consumption, and mortality of larvae from the two populations in both warm and cold seasons. Larvae from Mexico had higher thermal tolerances when collected in the boreal summer compared to the boreal winter, while no similar indication of seasonal acclimatization was seen in larvae from Peru. The lack of acclimatization in larvae of P. elegans from Peru may be related to recent thermal history, low selection for acclimatization due to irregular patterns of seasonal temperature change during ENSO events, or to different phylogeographic histories of Northern‐ and Southern‐hemisphere populations.     

Habitat Selection and Home Range Dynamics of Eastern Spotted Skunks in the Ouachita Mountains,Arkansas, USA

ABSTRACT Since the 1940s, eastern spotted skunks (Spilogale putorius) have declined dramatically throughout the Midwest. One hypothesis for the decline is the loss of suitable habitat, although little is known about the ecological requirements of this species. To elucidate seasonal home range and habitat selection by eastern spotted skunks, we conducted telemetry-based field work in the Ouachita Mountains of western Arkansas, USA. During 2 years of field work, we collected day- and nighttime radiolocations for 33 eastern spotted skunks. We used kernel-based utilization distributions, volume of intersection indices, and weighted compositional analysis to evaluate seasonal home range dynamics and habitat selection. Although we found moderate adult male site fidelity, there were large seasonal differences in home range size, with ranges of between 76 ha and 175 ha (± 22–62 SE) during summer, fall, and winter, and home ranges of 866 ha (± 235 SE) during spring. Male home range increases in the spring were likely caused by questing behavior in search of reproductive females. Females maintained home ranges of 54 ha to 135 ha (± 7–30 SE) and moderate site fidelity during all seasons. During each season, we observed selection of young shortleaf pine (Pinus echinata) and hardwood stands over other available cover types, likely due to a preference for a dense, complex understory and a closed canopy overstory to reduce predation risk. Most habitats in the study region were managed for an herbaceous understory and an older, more open canopy, in part to benefit red-cockaded woodpecker (Picoides borealis) populations. Thus, if simultaneous management for these 2 vertebrates is a goal, a balance of early and late successional habitat should be reached.     

Plant diversity in three types of hedgerows adjacent to cropfields

The farming landscape of eastern Canada is dotted with three main types of hedgerows: (1) natural woody, (2) planted woody and (3) herbaceous. The objective of this study was to compare the value of these habitats as a repository of plant biodiversity in agricultural areas of southern Quebec. The overall plant diversity was higher in natural hedgerows and they contained more plant species of conservation values than other hedgerow types. Plant species richness per quadrat was, however, higher in planted woody hedgerows, and together with the species composition, lead to the conclusion that planted hedgerows in their entirety consisted of an ecotone type of vegetation such as is found in field edges which usually support high plant diversity and productivity but where transient plant species predominate. Consequently, this study indicated that natural hedgerows fare better than planted hedgerows in terms of diversity of plants of conservation interest. In spite of that, planted woody hedgerows contained plant (and bird) species of some interest and should be favoured over more desolate herbaceous hedgerows. In areas where hedgerows were removed and are not re-establishing naturally, a mixture of deciduous trees and conifers should be encouraged in further windbreak planting programs so as to conciliate both the conservation and agronomic objectives. Furthermore, management practices should optimise the growth of establishing plants of conservation values.     

Evidence of a sex-linked diapause response in Papilio glaucus subspecies and their hybrids

ABSTRACT. Pupal diapause in the eastern tiger swallowtail. Papilio glaucus L., is obligatory or facultative depending on subspecies. The southern subspecies, P. g. glaucus has a facultative diapause, induced by a larval exposure to short photoperiods. In the northern subspecies. P.g. canadensis , diapause is obligatory, occurring in each generation. F*** hybrids inherit the diapause response of their father or respond differently from either parent. The incidence of diapause in hybrids was associated with sex, indicating that the diapause response may be determined by an X-linked gene.     

Vertical distribution of Pleuromamma (Copepoda: Metridinidae) across the eastern North Pacific Ocean

Vertical distributions of six species of Pleuromamma at ten stations across the eastern North Pacific Ocean from Honolulu to San Diego were determined from oblique Longhurst-Hardy Plankton Recorder tows to 650 m (350–450 m in the California Current). Vertical resolution was 20 m below 200 m and 5–10 m above. There was considerable overlap in surface layer distributions at night among all co-occurring species; daytime distributions showed less overlap. All species generally occurred deeper both day and night as distance offshore increased. The proportion of a species' population that remained at daytime depths during the night decreased with distance offshore. Warm water species penetrated into the California Current and nearshore region to a much greater extent than cool water species entered central gyre waters.     

Zonal plant communities of the Ribesalbes‐Alcora Basin (La Rinconada mine,eastern Spain) during the early Miocene

Changes in lobule morphology in Radula subgenus Cladoradula show liverworts have the capacity for dramatic, relatively rapid morphological change by heterochrony. In individuals of R. bipinnata, R. boryana and R. tenax, lobules on secondary and tertiary shoots are progenetic with respect to lobules on primary shoots, in that the slope of the relationship between growth duration and shape does not change. However, in R. campanigera, lobules on secondary and tertiary branches exhibit different slopes from primary branches, but have the same growth duration, a pattern consistent with neoteny. The trajectory of allometric growth is extended or truncated in different species compared with outgroup and ancestral nodes. Changes in duration of lobule growth explain 85% of variation in lobule shape between species. Species are related by relatively shallow nodes in the crown of the Radula subgenus Cladoradula clade, suggesting that divergence and associated heterochronic changes have occurred relatively recently. The rapid morphological diversification in the crown contrasts with the relative stasis between the ancestral node and R. brunnea, the outgroup used in this analysis. A robust primary axis may be required to hold shoots away from vertical surfaces to maximize light interception, and hypermorphosis in lobule ontogeny could be a by‐product of the longer growth durations required to build axes sufficiently large to perform this structural role. Alternatively, the large auriculate lobules could function in external water transport systems by providing continuity of surfaces for solute transport via capillary action. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 153–175.     

Bottom Communities of Semyachik Lagoon (Kronotskii Biosphere Reserve, Eastern Kamchatka)

Bottom communities of Potamogeton filiformis,Zostera marina+ Z. japonica+ Macoma balthica, Enteromorpha prolifera, and a stony block–boulder intertidal community were distinguished in Semyachik Lagoon. The macrobenthos associated with these communities is described. Generally, the biomass and occurrence frequency indices of the macrozoobenthic communities of the lagoon are an order of magnitude lower than those of macrophytobenthic communities (Kafanov, Plekhov, 1998); therefore, they do not play a significant role in bottom community structure. With the exception of the stony block–boulder intertidal community, their spatial distribution is entirely determined by the distribution of underwater vegetation, which is completely controlled by the geomorphological and hydrological features of the lagoon.     

Role of root systems of eastern larch and white spruce in response to flooding

Abstract. Soil flooding causes rapid reductions in transpiration, stomatal conductance and photosynthesis of many woody plants, which can decrease growth and ultimately result in plant death. This study was conducted to determine the role of the root system in the flooding response. Eastern larch ( Larix laricina ) seedlings were grown in Plexiglas tubes in which water uptake by flooded and unflooded roots was measured independently. Further flooding studies were conducted with eastern larch and white spruce ( Picea glauca ) in which stems were girdled. Root hydraulic properties were analysed using pressure-flow relationships. Transpiration rates of partially flooded plants declined more slowly than fully-flooded plants. Water uptake by unflooded roots of partially flooded seedlings increased momentarily with flooding. After lOd, flooding caused little change in root hydraulic conductance, a decrease in root system reflection coefficient, and an increase in osmotic permeability. Stem girdling had little effect on stomatal conductance and transpiration in comparison to flooding effects. The response of plant tops to flooding appears to be xylem-mediated and in proportion to the amount of root system flooded. Root hydraulic conductance appears to be unaffected by flooding except for a possible temporary increase on the first day following flooding treatments.