The Atacama toad (Rhinella atacamensis) exhibits an unusual clinal pattern of decreasing body size towards more arid environments

BMC Zoology ◽  
2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Felipe Durán ◽  
Marco A. Méndez ◽  
Claudio Correa
Keyword(s):  
Body Size ◽  
Geographic Variation ◽  
Water Availability ◽  
Size Variation ◽  
Mean Annual Precipitation ◽  
Arid Environments ◽  
Theoretic Approach ◽  
Adult Size ◽  
The North ◽  
Data Support

Abstract Background The causes of geographic variation of body size in ectotherms have generally been attributed to environmental variables. Research in amphibians has favored mechanisms that involve water availability as an explanation for the geographic variation of body size. However, there are few studies at intraspecific level on amphibians that inhabit desert or semi-desert environments, where hydric restrictions are stronger. Here, we describe and inquire as to the causes of the geographic variation of body size in the semi-desert toad Rhinella atacamensis, a terrestrial anuran that is distributed over 750 km along a latitudinal aridity gradient from the southern extreme of the Atacama Desert to the Mediterranean region of central Chile. We measured the snout-vent length of 315 adults from 11 representative localities of the entire distribution of the species. Then, using an information-theoretic approach, we evaluate whether the data support eight ecogeographic hypotheses proposed in literature. Results Rhinella atacamensis exhibits a gradual pattern of decrease in adult body size towards the north of its distribution, where the climate is more arid, which conforms to a Bergmann’s cline. The best model showed that the data support the mean annual precipitation as predictor of body size, favoring the converse water availability hypothesis. Conclusions Most studies in amphibians show that adult size increases in arid environments, but we found a converse pattern to expected according to the hydric constraints imposed by this type of environment. The evidence in R. atacamensis favors the converse water availability hypothesis, whose mechanism proposes that the foraging activity determined by the precipitation gradient has produced the clinal pattern of body size variation. The variation of this trait could also be affected by the decreasing productivity that exists towards the north of the species distribution. In addition, we found evidence that both pattern and mechanism are independent of sex. Lastly, we suggest that behavioral traits, such as nocturnal habits, might also play an important role determining this differential response to aridity. Therefore, the support for the converse water availability hypothesis found in this study shows that amphibians can respond in different ways to water restrictions imposed by arid environments.

scholarly journals High Resolution of Water Availability for Emilia-Romagna Region over 1961–2015

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
F. Cervi ◽  
M. M. Nistor
Keyword(s):  
Water Availability ◽  
Soil Surface ◽  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
North East ◽  
The North ◽  
Precipitation Decrease ◽  
Normal Period ◽  
Emilia Romagna Region ◽  
Annual Water

In this study, monthly time series of precipitations and temperatures from 1024 controlled and homogeneous meteorological stations located in the Emilia-Romagna region (northern Italy) are processed in order to assess potential climate changes that occurred during the period 1961–2015. Normal period as baseline between 1961 and 1990 (1990s) and recent period between 1991 and 2015 (2010s) were adopted in this study to analyse the possible effect of climate change on water availability during long-term period. Based on monthly and annual temperature (TT), precipitation (PP), and potential (ET0), the actual evapotranspiration (AET0) and water availability (WA) were computed at high spatial resolution. Between the two analysed periods, during the 2010s, it was found an increase in the maximum mean annual temperature by 1.08°C while the maximum mean annual precipitation saw a slight decrease (from 2222 mm to 2086 mm). The precipitation decrease is more intense in the South and West sectors of area (8%) and mainly depends on negative changes taking place during the winter and the beginning of spring (from December to March). The maximum mean annual ET0 and AET0 reached values of 663 mm and 565 mm during the 1990s, while during the 2010s, the found values were 668 mm and 572 mm, respectively. Because of the decrease in precipitation and increase in the ET0 and AET0, the WA (the proportion of precipitation that is available at the soil surface for subsequent infiltration and runoff processes) shows a reduction (about 10–20%) in the whole region, with exception of the North-East part of the Emilia-Romagna region. The decrease in the mean annual water availability induces severe issues concerning the water resources management across the whole Emilia-Romagna region.

Dichroplus vittatus(Orthoptera: Acrididae) follows the converse to Bergmann's rule although male morphological variability increases with latitude

2007 ◽  
Vol 97 (1) ◽  
pp. 69-79 ◽  
Author(s):  
C.J. Bidau ◽  
D.A. Martí
Keyword(s):  
Body Size ◽  
Morphological Variability ◽  
Size Variation ◽  
Bergmann’S Rule ◽  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
South American ◽  
Bergmann's Rule ◽  
Number Of Factors ◽  
Positive Correlations

AbstractGeographic body size variation was analysed in males and females of 19 populations of the South American grasshopperDichroplus vittatusBruner spanning 20 degrees of latitude and 2700 m of altitude. Using mean and maximum body length of each sex and factors obtained from principal components analyses of six morphometric linear characters it was shown thatD. vittatusfollowed the converse to Bergmann's rule latitudinally but not altitudinally where no significant trends were observed. For males, variability of body size increased with latitude but not with altitude. Both types of trends were significantly correlated with mean annual temperature and minimum annual temperature (positive correlations), and two estimators of seasonality, the coefficients of variation of mean annual temperature (negative) and mean annual precipitation (positive). Some allometric relationships also showed geographic variation. It is suggested that the observed decrease in size with latitude together with the increase in morphological variability is a consequence of a number of factors: the shortening of the growing season southwards; the increasing seasonality and climatic unpredictability; and the fact that the species exhibits protandry which contributes to smaller and more variable size in males and smaller but more constant body size in females.

scholarly journals Rapid genomic expansion and purging associated with habitat transitions in a clade of beach crustaceans (Haustoriidae: Amphipoda)

2020 ◽  
Author(s):  
Zachary B. Hancock ◽  
Faith O. Hardin ◽  
Archana Murthy ◽  
Andrew Hillhouse ◽  
J. Spencer Johnston
Keyword(s):  
Body Size ◽  
Genome Size ◽  
Size Variation ◽  
Data Availability ◽  
Genome Size Variation ◽  
The North ◽  
Physiological Constraint ◽  
Line Elements ◽  
The Relationship ◽  
Genomic Expansion

AbstractGenome sizes vary by orders of magnitude across the Tree of Life and lack any correlation with organismal complexity. Some crustacean orders, such as amphipods, have genome sizes that correlate with body size, temperature, and water depth, indicating that natural selection may constrain genome sizes due to physiological pressures. In this study, we examine the relationship between genome size, repetitive content, and environmental variables on a clade of sand-burrowing amphipods (Haustoriidae) that are distributed across the Gulf of Mexico and the North Atlantic. We uncover a 6-fold genome size variation within a clade that is less than 7 million years old. Unlike previous studies, we find no correlation between genome size and latitude, but do uncover a significant relationship between genome size and body length. Further, we find that the proportion of repetitive content predicts genome size, and that the largest genomes appear to be driven by expansions of LINE elements. Finally, we find evidence of genomic purging and body size reduction in two lineages that have independently colonized warm brackish waters, possibly indicating a strong physiological constraint of transitioning from surf-swept beaches to protected bays.Significance StatementThe evolution of genome size has been a long-standing puzzle in biology. In this work, we find that genome sizes may be driven by different selection regimes following shifts to a new habitat. Dramatic genome size changes can occur rapidly, in only a few million years.Data Availability StatementRaw data sheets have been deposited on Dryad: SUBMITTED. Raw sequence reads are available at from NCBI under Bioproject SUBMITTED.

Size matters: systematic and ecological implications of allometry in the responses of chironomid midge morphological ratios to experimental temperature manipulations

2005 ◽  
Vol 83 (4) ◽  
pp. 553-568 ◽  
Author(s):  
Brendan G McKie ◽  
Peter S Cranston
Keyword(s):  
Body Size ◽  
Phylogenetic Reconstruction ◽  
Size Variation ◽  
Adaptive Significance ◽  
Adult Size ◽  
Allometric Relationships ◽  
Terrestrial Environment ◽  
Environmental Regimes ◽  
Wide Range ◽  
Ecological Implications

Separated populations of wide-ranging ectothermic species may be subjected to differing ambient environmental regimes, with consequences for adult size and related allometric characteristics. We investigated effects of environmentally induced size variation in freshwater Australian Chironomidae (Diptera) on several morphometric ratios used to account for such variation in taxonomic classification. Echinocladius martini Cranston, 2000 (Orthocladiinae) and Australopelopia prionoptera Cranston, 2000 (Tanypodinae) larvae were sampled from tropical and temperate populations separated by approximately 1800 km, and reared to adult at temperatures representing the continent-wide range encountered by these species. Additionally, adults were sampled regularly from a field population to assess seasonal variation. Body size was related inversely to rearing temperature for both species. Nonlinear (allometric) relationships were observed consistently between body size and ratios pertaining to the antennae (AR, the ratio of the terminal to subapical flagellomeres) and legs (BV, the ratio of proximal segments to distal tarsomeres), demonstrating that these ratios inadequately factor out within-species, size-related divergence. Responses of other ratios varied erratically with sex, species, and population. We advocate cautious use of these ratios in taxonomy and phylogenetic reconstruction. We discuss possible adaptive significance of allometry in the male antennae related to the "tuning" of sound-sensitive structures to the expected terrestrial environment encountered at emergence.

scholarly journals DO LATITUDE, ELEVATION, TEMPERATURE, AND PRECIPITATION INFLUENCE BODY AND CLUTCH SIZES OF FEMALE COMMON FIVE-LINED SKINKS, PLESTIODON FASCIATUS (LINNAEUS, 1758)?

2020 ◽  
pp. 32-41
Author(s):  
Jake S. Morrissey ◽  
Brandon Barr ◽  
Andrew E. Austin ◽  
Lauren R. Babcock ◽  
Robert Powell
Keyword(s):  
Body Size ◽  
Mean Annual Precipitation ◽  
Eastern North America ◽  
Mean Annual Temperature ◽  
Negatively Associated ◽  
The North ◽  
Female Body Size ◽  
Temperature And Precipitation ◽  
Plestiodon Fasciatus ◽  
Positive Effect

Common Five-lined Skinks (Plestiodon fasciatus) have an extensive distribution that includes much of eastern North America. We examined 490 female specimens (274 with putative clutch sizes) from throughout the range to see if latitude, elevation, mean annual temperature, and/or mean annual precipitation affected body or clutch sizes. We predicted that larger females would produce larger clutches, latitude and elevation would negatively affect both body and clutch sizes, and that temperature and precipitation would exert a positive effect. Our results did not consistently support those predictions. Body size was positively associated with latitude, negatively associated with temperature, and not associated with elevation or precipitation. Clutch size was not related to female body size, but in most instances was positively associated with temperature and precipitation but negatively associated with elevation and latitude. Effectively K-selected in the North and r-selected in the South, body and clutch sizes in this species appear to be responding to different select.

scholarly journals Seasonal body size reductions with warming covary with major body size gradients in arthropod species

2017 ◽  
Vol 284 (1851) ◽  
pp. 20170238 ◽  
Author(s):  
Curtis R. Horne ◽  
Andrew G. Hirst ◽  
David Atkinson
Keyword(s):  
Body Size ◽  
Size Variation ◽  
Seasonal Temperature ◽  
Adult Size ◽  
Aquatic Species ◽  
Terrestrial Species ◽  
Total Percentage ◽  
Arthropod Species ◽  
Seasonal Temperature Variation ◽  
Developmental Conditions

Major biological and biogeographical rules link body size variation with latitude or environmental temperature, and these rules are often studied in isolation. Within multivoltine species, seasonal temperature variation can cause substantial changes in adult body size, as subsequent generations experience different developmental conditions. Yet, unlike other size patterns, these common seasonal temperature–size gradients have never been collectively analysed. We undertake the largest analysis to date of seasonal temperature-size gradients in multivoltine arthropods, including 102 aquatic and terrestrial species from 71 global locations. Adult size declines in warmer seasons in 86% of the species examined. Aquatic species show approximately 2.5-fold greater reduction in size per °C of warming than terrestrial species, supporting the hypothesis that greater oxygen limitation in water than in air forces aquatic species to exhibit greater plasticity in body size with temperature. Total percentage change in size over the annual cycle appears relatively constant with annual temperature range but varies between environments, such that the overall size reduction in aquatic-developing species (approx. 31%) is almost threefold greater than in terrestrial species (approx. 11%). For the first time, we show that strong correlations exist between seasonal temperature–size gradients, laboratory responses and latitudinal–size clines, suggesting that these patterns share common drivers.

Eco-Geographic Variation in Size and Sexual Dimorphism in Sugar Gliders and Squirrel Gliders (Marsupialia: Petauridae)

1996 ◽  
Vol 44 (1) ◽  
pp. 19 ◽  
Author(s):  
DG Quin ◽  
AP Smith ◽  
TW Norton
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Geographic Variation ◽  
Multiple Regression ◽  
Primary Productivity ◽  
Isolation By Distance ◽  
Size Variation ◽  
Climatic Variables ◽  
Regression Analyses ◽  
Distance Model

Geographic variation iri body size and sexual dimorphism, as determined by measurements of condylo-basal length, was investigated in the sugar glider (Petaurus breviceps) and the squirrel glider (P. norfolcensis). Correlation and multiple regression analyses were employed to determine whether geographic or climatic variables accounted for more of this size variation. The effects of age and sex were removed from analyses prior to applying statistical techniques. Numerous geographic and climatic variables were correlated with size variation in both species. Both species followed a clinal change in body size consistent with Bergmann's rule (i.e. both species were larger in the south of their ranges where temperatures are colder). One geographic variable, latitude, and three climatic variables representing temperature, precipitation and seasonality, were then selected for multiple regression analyses. Latitude accounted for more of this size variation (20-28%) in P. breviceps than climatic variables in four multiple regression models (considering two age and two sex classes). This result indicated that an isolation-by-distance model was operating in this species which was attributed to the oceanic barriers between the Australian mainland and New Guinea and Tasmania, causing genetic differentiation between isolated populations. Once latitude was removed from the analyses, temperature accounted for more of the variation (18-24%) in body size in three regressions, whilst precipitation (11%) contributed significantly to the remaining model. This result was interpreted as an adaptation to ambient temperature following Bergmann's rule. When using both geographic and climatic variables, latitude accounted for more size variation (47-69%) than climatic variables in two regressions for P. norfolcensis, whilst seasonality accounted for more variation (26-46%) in the remaining two regressions. When latitude was excluded From the analyses, seasonality (body size decreases with increasing seasonality) accounted for more variation in size in three of four regressions (26-46%), whilst precipitation (60%) accounted for the most variation in the fourth regression. These findings for P. norfolcensis suggested that large body size may be an advantage in aseasonal environments where climates and therefore foods are less predictable. Latitude and precipitation both contributed significantly to the degree of sexual dimorphism exhibited across the range of P. breviceps, suggesting that an isolation-by-distance model and primary productivity account for some of the change in sexual dimorphism in this species. Both these variables were more important than temperature and average sexual dimorphism was greater in the tropics. The relationship with primary productivity implies that in areas where food is more abundant, males attempt to grow larger in order to enhance fighting ability for access to food and mates. In contrast, females channel extra energy towards offspring production, not body size, in order to minimise energy costs during reproduction. Character displacement did not appear to influence body size variation in the two Petaurus species.

scholarly journals Independent evolution towards larger body size in the distinctive Faroe Island mice

2021 ◽  
Author(s):  
Ricardo Wilches ◽  
William H Beluch ◽  
Ellen McConnell ◽  
Diethard Tautz ◽  
Yingguang Frank Chan
Keyword(s):  
Body Size ◽  
Meta Analysis ◽  
Small Body ◽  
Laboratory Mouse ◽  
Large Body ◽  
Natural Populations ◽  
Size Variation ◽  
Phenotypic Traits ◽  
Island Population ◽  
Multiple Loci

Abstract Most phenotypic traits in nature involve the collective action of many genes. Traits that evolve repeatedly are particularly useful for understanding how selection may act on changing trait values. In mice, large body size has evolved repeatedly on islands and under artificial selection in the laboratory. Identifying the loci and genes involved in this process may shed light on the evolution of complex, polygenic traits. Here, we have mapped the genetic basis of body size variation by making a genetic cross between mice from the Faroe Islands, which are among the largest and most distinctive natural populations of mice in the world, and a laboratory mouse strain selected for small body size, SM/J. Using this F2 intercross of 841 animals, we have identified 111 loci controlling various aspects of body size, weight and growth hormone levels. By comparing against other studies, including the use of a joint meta-analysis, we found that the loci involved in the evolution of large size in the Faroese mice were largely independent from those of a different island population or other laboratory strains. We hypothesize that colonization bottleneck, historical hybridization, or the redundancy between multiple loci have resulted in the Faroese mice achieving an outwardly similar phenotype through a distinct evolutionary path.

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