Biogeographic Patterns in Life-History Traits of the Yellow Clam, Mesodesma mactroides, in Sandy Beaches of South America

2006 ◽  
Vol 224 ◽  
pp. 872-880 ◽  
Author(s):  
Sandra Fiori ◽  
Omar Defeo
2021 ◽  
pp. 1-7
Author(s):  
Ken S. Toyama ◽  
Christopher K. Boccia

Abstract Opposing life history strategies are a common result of the different ecological settings experienced by insular and continental species. Here we present a comprehensive compilation of data on sexual size dimorphism (SSD) and life history traits of Microlophus, a genus of lizards distributed in western South America and the Galápagos Islands, and test for differences between insular and continental species under life history theory expectations. Contrary to our predictions, we found no differences in SSD between localities or evidence that Microlophus follows Rensch’s rule. However, as expected, head dimensions and maturity sizes were significantly larger in insular species while continental species had larger clutches. Our results show that Microlophus exhibits some of the patterns expected from an island-mainland system, but unexplained patterns will only be resolved through future ecological, morphological and behavioural studies integrating both faunas.


Author(s):  
Omar Defeo ◽  
Gastón Martínez

Demographic and life history characteristics of the intertidal isopod Excirolana braziliensis (Isopoda: Cirolanidae) were compared between populations of two exposed sandy beaches with contrasting morphodynamics (reflective vs dissipative) during 22 consecutive months. Most population processes and life history traits did not give support for the ‘habitat harshness hypothesis’ (HHH): abundance of males, females, ovigerous females and juveniles was significantly higher at the reflective beach population, which also presented higher growth rates in size and weight with respect to the dissipative beach population. No significant differences in weight-at-length were found between beaches. Among the compared parameters, only the lower natural mortality rates at the dissipative beach gave support for the HHH. The results were not consistent with a previous analysis of Excirolana braziliensis along Pan-American beaches, which showed that this isopod occurs almost invariably in fine sands of tropical and temperate beaches. The results give strong support to recent findings that show that in macrofauna species capable of sustaining large populations across a wide spectrum of physical conditions, such as Excirolana braziliensis, beach morphodynamics should not be considered the primary factor affecting abundance and life history traits. Instead, our results reinforce the view that sandy beach populations are controlled by the intertwined forces of biotic and abiotic factors operating together.


2011 ◽  
Vol 62 (7) ◽  
pp. 790 ◽  
Author(s):  
Nicole C. Barbee ◽  
Robin Hale ◽  
John Morrongiello ◽  
Andy Hicks ◽  
David Semmens ◽  
...  

Applying uniform population models and management strategies to widespread species can be ineffective if populations exhibit variable life histories in response to local conditions. Galaxias maculatus, one of the world’s most widely distributed fish species, occurs in a broad range of habitats and is highly adaptable, making it an ideal species for examining variation in life history traits across large geographic scales. Here, we examine the spawning biology and early life history of diadromous G. maculatus in coastal rivers in Victoria, Australia, and compare them to other populations throughout its range. We predicted that traits associated with these critical life stages, especially those that respond to environmental conditions that vary geographically, such as seasonal cues and temperature, are likely to vary across large spatial scales. We found that spawning occurs later in Victoria than in New Zealand (NZ) and South America, but migration back to rivers occurs at the same time in Victoria and NZ, but not South America. G. maculatus returning to rivers are also smaller and younger in Victoria than those in NZ. Other traits, like some attributes of spawning schools and spawning habitats, did not vary across large scales. Researchers and managers should be cautious when making broad assumptions about the biology of widely distributed species.


2012 ◽  
Vol 60 (4) ◽  
pp. 473-484 ◽  
Author(s):  
Marcelo Petracco ◽  
Ricardo Silva Cardoso ◽  
Thais Navajas Corbisier ◽  
Alexander Turra

The state of the art of the studies on the production of Brazilian sandy beach macrofauna was analyzed on the basis of the data available in the literature. For this purpose, the representativeness of the production dataset was examined by latitudinal distribution, degree of exposure and morphodynamic state of beaches, taxonomic groups, and methods employed. A descriptive analysis was, further, made to investigate the trends in production of the more representative taxonomic groups and species of sandy beach macrofauna. A total of 69 macrofauna annual production estimates were obtained for 38 populations from 25 studies carried out between 22º56'S and 32º20'S. Production estimates were restricted to populations on beaches located on the southern and southeastern Brazilian coast. Most of the populations in the dataset inhabit exposed dissipative sandy beaches and are mainly represented by mollusks and crustaceans, with a smaller number of polychaetes. The trends in production among taxonomic groups follow a similar pattern to that observed on beaches throughout the world, with high values for bivalves and decapods. The high turnover rate (P/B ratio) of the latter was due to the presence of several populations of the mole crab Emerita brasiliensis, which can attain high values of productivity, in the dataset. Most of the studies focus on the comparison of production and, especially, of P/B ratio according to life history traits in populations of the same species/taxonomic group. Despite the importance of life history-production studies, other approaches, such as the effect of man-induce disturbances on the macrofauna, should be undertaken in these threatened environments.


Polar Biology ◽  
2020 ◽  
Vol 43 (10) ◽  
pp. 1643-1654 ◽  
Author(s):  
Facundo M. Llompart ◽  
Daniel A. Fernández ◽  
Daniel Aureliano ◽  
Mario La Mesa

2011 ◽  
Vol 68 (2) ◽  
pp. 288-303 ◽  
Author(s):  
Jennifer E. Caselle ◽  
Scott L. Hamilton ◽  
Donna M. Schroeder ◽  
Milton S. Love ◽  
Julie D. Standish ◽  
...  

Geographic variation in ecological and environmental factors may lead to intraspecific differences among populations. For the California sheephead ( Semicossyphus pulcher ), an important predator in kelp forests and a target of commercial and recreational fisheries, we evaluated the degree to which different populations exhibited variation in density, demography, and life history traits. We assessed biogeographic patterns of abundance through underwater visual census at 39 sites spanning a major portion of the species range (southern California, USA, to Baja California, Mexico) and made collections from seven focal sites to investigate geographic differences in demography and life histories. California sheephead densities were significantly greater in the southern part of their range and at offshore islands than along the mainland coast. At the focal sites, we found significant spatial variation in density, fecundity, size structure, growth rates, annual survivorship, and the timing of maturation and sex change. Density- and temperature-dependent effects helped to explain the intraspecific differences in these parameters. Studies such as this one will allow for demographic plasticity to be incorporated into future stock assessments. Management of temperate reef fishes may best be achieved on smaller spatial scales as we increase our understanding of geographic variation among populations.


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