Key Life History Stages Research Articles

Retraction Note: Advancements in morphometric differentiation: a review on stock identification among fish populations

Identifying intraspecific units or stocks of a species with unique morphological characteristics has now become more powerful and enables a better management of these subunits of species and ensures better management and conservation of the fishery resources. These morphometric characteristics typically show ontogenic changes in body shape particularly rapid at key life history stages. For about the past 50 years, traditional multivariate morphometrics, accounting for variation in size and shape, have successfully discriminated many fish stocks throughout the world, however, they have always been criticized because of several biases and weaknesses. To contribute to the advancement of fish stock identification, a new technology based on “Truss Network System” has emerged as a new tool with more effective strategies for descriptions of shape, better data collection and diversified analytical tools. In the present communication, recent developments made in the discipline of morphometric differentiation in body shape among fish populations are briefly reviewed and it appears that the truss based techniques has now been proved to be more effective than manual distance measurement for the management of fishery resources throughout the world. However in India, these techniques have not been commonly applied in fisheries research to discriminate fish stocks. The study expands the potential through various advancements in morphometric differentiation analysis which could serve as a tool for stock identification among fish populations.

Regeneration as a novel method to culture marine ornamental sabellids

Collection of live invertebrates from coral reefs has increased dramatically over the past two decades in response to the growing marine aquarium industry, and currently, more than 500 species (excluding corals) are traded globally. Aquaculture of ornamental species is deemed a priority solution in mitigating the effects of wild collection but expanding the range of species is limited by bottlenecks at key life history stages. A novel culture method for ornamental sabellids, which utilises their outstanding regenerative capacity in a process similar to coral ‘fragging’, has been developed and survivorship after regenerative development assessed. Sabella pavonina, a temperate species found around the UK, was used as a model to develop a culture technique which was subsequently transferred to a tropical species of Sabellastarte. Survivorship of S. pavonina was high (≥80%) in individuals which had been cut into as many as eight fragments and all fragments completed regenerative development within a four week period. Sabellastarte species exhibited ≥75% survivorship when cut into just two fragments, but higher mortality was recorded with increasing number of cuts, with only 20% of fragments from individuals cut into eighths surviving the duration of the experiment. Both test species were capable of regenerating cephalically and caudally within a four week period. Caudal regeneration involved the healing of the cut surface, reconstruction of the pygidium and subsequent segment addition, while cephalic regeneration was a more complex process of wound healing, reconstruction of a new mouth and the development of the branchial crown structure. It is concluded that differences in survivorship between S. pavonina and Sabellastarte sp. could be attributed to either infection due to sub-optimal water quality in the test tanks, or species-specific differences in the area of wound size in relation to the length of the fragment. Optimisation of survivorship and the speed of regenerative growth could be improved with the enhancement of the culture system.

Investigating the production of sexual resting structures in a plant pathogen reveals unexpected self‐fertility and genotype‐by‐environment effects

The sexual stage of pathogens governs recombination patterns and often also provides means of surviving the off-season. Despite its importance for evolutionary potential and between-season epidemiology, sexual systems have not been carefully investigated for many important pathogens, and what generates variation in successful sexual reproduction of pathogens remains unexplored. We surveyed the sexually produced resting structures (chasmothecia) across 86 natural populations of fungal pathogen Podosphaera plantaginis (Ascomycota) naturally infecting Plantago lanceolata in the Åland archipelago, southwestern Finland. For this pathosystem, these resting structures are a key life-history stage, as more than half of the local pathogen populations go extinct every winter. We uncovered substantial variation in the level of chasmothecia produced among populations, ranging from complete absence to presence on all infected leaves. We found that chasmothecia developed within clonal isolates (single-strain cultures). Additionally, these clonal isolates all contained both MAT1-1-1 and MAT1-2-1 genes that characterize mating types in Ascomycetes. Hence, contrary to expectations, we conclude that this species is capable of haploid selfing. In controlled inoculations, we discovered that pathogen genotypes varied in their tendency to produce chasmothecia. Production of chasmothecia was also affected by ambient temperature (E) and by the interaction between temperature and pathogen genotype (G×E). These G, E and G×E effects found both at a European scale and within the Åland archipelago may partly explain the high variability observed among populations in chasmothecia levels. Consequently, they may be key drivers of the evolutionary potential and epidemiology of this highly dynamic pathosystem.

Conservation of coastal stingrays: seasonal abundance and population structure of the short-tailed stingray Dasyatis brevicaudata at a Marine Protected Area

AbstractLe Port, A., Lavery, S., and Montgomery, J. C. 2012. Conservation of coastal stingrays: seasonal abundance and population structure of the short-tailed stingray Dasyatis brevicaudata at a Marine Protected Area. – ICES Journal of Marine Science, 69: . Elasmobranch (shark, ray, and skate) populations around the world are in decline, and effective conservation measures are urgently needed. Marine Protected Areas (MPA) placed in locations important for key life-history stages may form part of an effective conservation strategy. In this context, we examined the seasonal abundance and population structure of the short-tailed stingray (Dasyatis brevicaudata) at an offshore MPA in northeastern New Zealand, and the reported use of this location as a mating ground. Diver surveys were conducted from 2004 to 2007 at the Poor Knights Islands Marine Reserve (PKIMR). During this time, we observed: (i) a substantial increase in adult and subadult numbers, particularly females during the suggested breeding season, and a corresponding increase in females bearing fresh mating scars; and (ii) large numbers of smaller (probably immature) D. brevicaudata individuals of both sexes from spring to autumn. These results suggest that the PKIMR acts as both a mating aggregation location and a nursery for this species. We suggest that for coastal stingrays such as D. brevicaudata, small MPAs may be effective at protecting key life-history stages, but that as movements outside of reserve boundaries also occur, additional management tools may also be necessary.

Projected soil temperature increase and seed dormancy response along an altitudinal gradient: implications for seed bank persistence under climate change

Background and aims Understanding the mechanistic effects of climate change on species key life-history stages is essential for predicting ecological responses. In fire-prone regions, long-term seed banks allow post-fire recovery and persistence of plant populations. For physically dormant species, seed bank longevity depends on the maintenance of dormancy which is controlled primarily by temperature. Successful inter-fire recruitment is rare and dormancy loss between fires produces a net loss to the seed bank. We assessed whether temperature increases related to climate change can affect seed dormancy and, potentially, seed bank longevity.

Seasonal variations in diet of arrow squid (Nototodarus gouldi): stomach content and signature fatty acid analysis

This study details the feeding ecology of arrow squid,Nototodarus gouldi, collected opportunistically from trawlers in waters south-east off Australia in 2007 and 2008. Combined stomach content and fatty acid (FA) signature analyses provided clear evidence of seasonal dietary shifts in prey composition. Teleost fish remains (mainly otoliths) were found in 67% of stomachs with the two mesopelagic planktivorous fish,Lampanyctodes hectorisandMaurolicus muelleridominating. Cephalopods and crustaceans were supplementary dietary components, with an increased representation in the diet over winter. Digestive gland lipid content was moderate (16.4 ± 8.4% wet weight) and was rich in triacylglycerol and monounsaturated fatty acids. Multivariate analysis of FA profiles grouped arrow squid with profiles of mesopelagic fish and cephalopods, thus supporting the findings of stomach content analysis. Seasonal differences in total lipid content were likely related to summer upwelling events and local changes in productivity, while intraspecific differences in lipid class and FA composition were related to seasonal differences of prey consumption. FA analyses also demonstrated dietary differences associated with gender, size and female maturation. Such relationships demonstrate that the diet ofN. gouldiis closely linked to prey size, abundance and availability and possibly also, to key life-history stages.

Ecological specialization in mycorrhizal symbiosis leads to rarity in an endangered orchid

Terrestrial orchid germination, growth and development are closely linked to the establishment and maintenance of a relationship with a mycorrhizal fungus. Mycorrhizal dependency and specificity varies considerably between orchid taxa but the degree to which this underpins rarity in orchids is unknown. In the context of examining orchid rarity, large scale in vitro and in situ germination trials complemented by DNA sequencing were used to investigate ecological specialization in the mycorrhizal interaction of the rare terrestrial orchid Caladenia huegelii. Common and widespread sympatric orchid congeners were used for comparative purposes. Germination trials revealed an absolute requirement for mycorrhisation with compatibility barriers to germination limiting C. huegelii to a highly specific and range limited, efficacious mycorrhizal fungus. DNA sequencing confirmed fidelity between orchid and fungus across the distribution range of C. huegelii and at key life history stages within its life cycle. It was also revealed that common congeners could swap or share fungal partners including the fungus associated with the rare orchid but not vice versa. Data from this study provides evidence for orchid rarity as a cause and consequence of high mycorrhizal specialization. This interaction must be taken into account in efforts to mitigate the significant extinction risk for this species from anthropogenically induced habitat change and illustrates the importance of understanding fungal specificity in orchid ecology and conservation.

Subtropical pupping ground for a cold-water shark

Porbeagle sharks ( Lamna nasus ) are large pelagic sharks apparently restricted to the cold temperate waters of the northern and southern hemispheres. Despite considerable knowledge of their biology, their pupping (birthing) grounds have never been identified. Pop-up archival transmission tags applied to 21 sharks off eastern Canada indicated that males and immature sharks of both sexes remained primarily on the continental shelf for periods of up to 348 days after tagging. However, mature female porbeagles migrated up to 2356 km through the winter, at depths down to 1360 m beneath the Gulf Stream, to a subtropical pupping ground in the Sargasso Sea. In addition to this pupping ground being well south of their documented range, the placement of such a key life history stage in international, largely unregulated waters poses problems for the conservation and management of a species that is largely fished in Canadian waters.

Novelties of the flowering plant pollen tube underlie diversification of a key life history stage.

The origin and rapid diversification of flowering plants has puzzled evolutionary biologists, dating back to Charles Darwin. Since that time a number of key life history and morphological traits have been proposed as developmental correlates of the extraordinary diversity and ecological success of angiosperms. Here, I identify several innovations that were fundamental to the evolutionary lability of angiosperm reproduction, and hence to their diversification. In gymnosperms pollen reception must be near the egg largely because sperm swim or are transported by pollen tubes that grow at very slow rates (< approximately 20 microm/h). In contrast, pollen tube growth rates of taxa in ancient angiosperm lineages (Amborella, Nuphar, and Austrobaileya) range from approximately 80 to 600 microm/h. Comparative analyses point to accelerated pollen tube growth rate as a critical innovation that preceded the origin of the true closed carpel, long styles, multiseeded ovaries, and, in monocots and eudicots, much faster pollen tube growth rates. Ancient angiosperm pollen tubes all have callosic walls and callose plugs (in contrast, no gymnosperms have these features). The early association of the callose-walled growth pattern with accelerated pollen tube growth rate underlies a striking repeated pattern of faster and longer-distance pollen tube growth often within solid pathways in phylogenetically derived angiosperms. Pollen tube innovations are a key component of the spectacular diversification of carpel (flower and fruit) form and reproductive cycles in flowering plants.

Sex-specific development of avian flight performance under experimentally altered rearing conditions

Numerous studies have examined predation risk resulting from the costs of impaired flight performance associated with many key life-history stages such as reproduction and migration. Interestingly, although avian nestlings experience multiple resourcebased physiological trade-offs and undergo considerable morphological and physiological changes during postnatal development, there is no data available on how nestlings manage the competing demands of growth and the development of flight ability at this critical life-history stage. We examined numerous morphological traits to determine which are responsible for variation in flight performance in juvenile European starlings (Sturnus vulgaris), a sexually size-dimorphic passerine. We then manipulated maternal quality during chick rearing (via feather clipping) to examine sex-specific sensitivity of fledgling flight performance to the quality of the rearing environment. Results suggest that the mechanics underlying variation in juvenile flight performance are relatively simple, being principally determined by the ratio of pectoral muscle mass to body mass (BM) and the surface area of the wings. Interestingly, although the maternal quality manipulation decreased BM and structural size in daughters, only the flight performance of sons was negatively affected. Our results suggest that a survival-related trait can be significantly affected in the larger sex when raised under stressful conditions. Furthermore, measuring only BM and structural size may not be sufficient in understanding how the sexes are affected by stressful rearing conditions in sexually size-dimorphic species. Key words: development, escape performance, european starling, flight ability, predation risk, sexual size dimorphism. [Behav Ecol]

Ecological fitness of a glyphosate-resistant Lolium rigidum population: Growth and seed production along a competition gradient

Repeated use of glyphosate has resulted in evolution of glyphosate-resistant Lolium rigidum populations in Australia. The relative growth, competitiveness and reproductive output of glyphosate resistant (R) and susceptible (S) L. rigidum phenotypes from a single population were compared in competition with wheat. Vegetative growth of R and S individuals was studied in response surface experiments in the glasshouse and seed production was measured using an additive neighbourhood design experiment conducted in pots outside during the normal growing season of L. rigidum in Australia. There were no significant differences in vegetative growth or competitiveness of the R and the S phenotypes. The mean weight of seeds produced by R plants was significantly greater than that produced by S individuals. In the absence of wheat and at tow wheat densities, S plants produced more seeds than R plants. However, at higher crop densities, differences in seed production were not significant. This is the first study to compare components of fitness at key life history stages for glyphosate R and S phenotypes isolated from a single weed population. The results presented indicate important differences in resource allocation during the reproductive stage for R and S phenotypes. Subtle differences in life history strategies may be manipulated by agronomic management to exploit the potential ecological fitness costs of the R phenotype. Further studies are required to provide a greater understanding of the occurrence and extent of fitness costs associated with glyphosate resistance. This knowledge can then be incorporated into models that simulate resistance evolution to design management strategies to prevent and/or contain the spread of glyphosate resistance. (C) 2006 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

Linking climate and physiology at the population level for a key life-history stage of turtles

Forthcoming climate change is expected to impact the global biota, particularly by altering range limits. However, the roles of early life stages in affecting biogeography and the impact of climate change on reptiles are both poorly understood. Fitness of neonatal reptiles depends greatly on energy reserves and body size, which themselves are affected by abiotic conditions in laboratory experiments performed during embryonic development and posthatching dormancy. To test whether these relationships between environment and physiology hold in nature, we conducted a 6-year field study on a natural northern population of red-eared slider turtles, Trachemys scripta elegans (Wied-Neuwied, 1839). Climatic conditions varied substantially and impacted offspring phenotypes. Consistent with bioenergetic predictions, cohorts that experienced warmer periods of posthatching dormancy had less dry residual yolk mass than similar-sized hatchlings that experienced cooler overwintering periods. Thus, global warming may exert adverse effects on turtle energy reserves important to fitness during crucial early life stages; this negative physiological impact may extend to other ectotherms with obligate, nonfeeding stages.

The population dynamics and life-history attributes of a Pterocarpus angolensis DC. population in the Northern Province, South Africa

This article examines the population dynamics and life-history attributes of a single P. angolensis population in the Northern Province, South Africa. An introduction to the use of matrix models in population biology is presented. A frequency distribution of diameters reveals a bimodal distribution of stems. Yearly diameter growth increases with age. It is, therefore, concluded that this bimodal size distribution is indicative of discrete recruitment events of permanent stems and not of an unstable population. Established trees and seedlings (suffrutices) can persist in the landscape by means of coppicing. A matrix model, combined with an elasticity analysis of the derived transition matrix is used to isolate key life-history stages. Life-history stages lying along the diagonal of the matrix have the highest elasticity values, emphasizing the importance of stem survivorship, as opposed to growth or fecundity, in the survival of this tree. Long-term survival greater than the life-span of a stem depends on seedling recruitment events. The model is also used to predict the outcome of two harvesting strategies on the future of the population. Some suggestions for management and priorities for future research are presented.