Offspring size variation in a hybrid zone of Australian frogs (Geocrinia laevis complex, Myobatrachinae)

1994 ◽  
Vol 15 (4) ◽  
pp. 343-350 ◽  
Author(s):  
Günter Gollmann ◽  
Birgit Gollmann
Keyword(s):  
Hybrid Zone ◽  
Egg Size ◽  
Parental Species ◽  
Size Variation ◽  
Offspring Size ◽  
Strongly Correlated ◽  
Local Populations ◽  
True Hybrid ◽  
Genetic Characters ◽  
Hatchling Size

AbstractTo describe variation in size of offspring across a hybrid zone between the myobatrachine frogs Geocrinia laevis and Geocrinia victoriana, the sizes of tadpoles hatching from egg masses collected in the field were measured. Hatchling size was strongly correlated with diameter of the blastula or gastrula (referred to here as "egg size"). Geocrinia victoriana had bigger offspring than G. laevis. Hybrids were generally intermediate between the two parental species in offspring size. However, the variation in size across the hybrid zone did not show a smooth cline or a distinct step coinciding with any of the sharp transitions found for behavioural or genetic characters. Variation within hybrid populations was not greater than in "pure" samples of the two species; these data correspond to findings of other studies which showed that this contact between G. laevis and G. victoriana is a "true hybrid zone" with panmictic local populations, not an overlap of the two species.

Within-clutch egg-size variation in a subsocial bug: the positional effect hypothesis

2006 ◽  
Vol 84 (11) ◽  
pp. 1540-1544 ◽  
Author(s):  
Shin-ichi Kudo
Keyword(s):  
Predation Risk ◽  
Clutch Size ◽  
Egg Size ◽  
Size Variation ◽  
Instar Nymph ◽  
Offspring Size ◽  
Egg Mass ◽  
Female Body Size ◽  
Positional Effect ◽  
Effect Hypothesis

If there are differences in predation risk among the offspring within a clutch, parents should allocate less resources to the offspring facing higher risk. Predation risk, and thus offspring size, may depend on the spatial position of individual offspring within a clutch. To test this positional effect hypothesis, I examined egg-size (egg-mass) variation in the subsocial bug Elasmucha signoreti Scott, 1874 (Hemiptera: Acanthosomatidae). In subsocial insects, including Elasmucha , in which females guard their clutches against predators by covering the clutch with their bodies, there are large differences in survival between offspring at the centre and at the periphery of the clutch. There was considerable variation in reproductive output among females; female body size was positively correlated with egg mass but not with clutch size. Females laid significantly lighter eggs in the peripheral, and thus more vulnerable, part of the clutch. No phenotypic trade-off between egg mass and clutch size was detected. Egg mass was positively correlated with hatched first-instar nymph mass. Thus, E. signoreti females seem to allocate their resources according to the different predation risks faced by the offspring within a clutch. I suggest that the positional effect hypothesis can generally be applicable to species whose females lay eggs in clutches and that the eggs suffer different mortality rates which depend on their spatial positions within the clutch.

Egg size variation as a function of environmental variability in parasitic trematodes

2000 ◽  
Vol 78 (4) ◽  
pp. 564-569 ◽  
Author(s):  
Robert Poulin ◽  
William J Hamilton
Keyword(s):  
Egg Size ◽  
Environmental Variability ◽  
Temporal Stability ◽  
Size Variation ◽  
Intraspecific Variability ◽  
Environmental Stability ◽  
Offspring Size ◽  
Trematode Species ◽  
Environmental Predictability ◽  
Terrestrial Habitats

Environmental predictability is often assumed to select for variability in egg size or offspring size, since a greater variance in offspring size may insure that, on average, a greater proportion of offspring will survive whatever the conditions experienced. In a comparative analysis across 747 species of parasitic trematodes, we examined the relationship between intraspecific variability in egg size and three predictors of environmental stability: the type of definitive host, the type of habitat in which parasite eggs are released, and latitude. Although trematode species using ectothermic hosts and (or) releasing eggs in terrestrial habitats tended to have more variable egg sizes than species using endothermic hosts and (or) releasing eggs in water, the trend was not significant, even when controlling for phylogenetic influences. Latitude correlated strongly and negatively with variability in egg sizes among trematode species releasing their eggs in terrestrial habitats, whether or not phylogenetic effects were removed. No relationship was found among species releasing their eggs in water. We propose that spatial heterogeneity of the external environment, and not its temporal stability, has played an important role in shaping intraspecific variability in egg sizes in parasitic trematodes.

Elevated nest predation risk promotes offspring size variation in birds with prolonged parental care.

2019 ◽  
Author(s):  
Gretchen F. Wagner ◽  
Emeline Mourocq ◽  
Michael Griesser
Keyword(s):  
Predation Risk ◽  
Reproductive Cycle ◽  
Perceived Risk ◽  
Nest Predation ◽  
Bird Species ◽  
Size Variation ◽  
Egg Laying ◽  
Offspring Size ◽  
Natural Predation ◽  
Risk Spreading

Predation of offspring is the main cause of reproductive failure in many species, and the mere fear of offspring predation shapes reproductive strategies. Yet, natural predation risk is ubiquitously variable and can be unpredictable. Consequently, the perceived prospect of predation early in a reproductive cycle may not reflect the actual risk to ensuing offspring. An increased variance in investment across offspring has been linked to breeding in unpredictable environments in several taxa, but has so far been overlooked as a maternal response to temporal variation in predation risk. Here, we experimentally increased the perceived risk of nest predation prior to egg-laying in seven bird species. Species with prolonged parent-offspring associations increased their intra-brood variation in egg, and subsequently offspring, size. High risk to offspring early in a reproductive cycle can favour a risk-spreading strategy particularly in species with the greatest opportunity to even out offspring quality after fledging.

Effects of Predation and Trophic Conditions on the Reproduction of Tylototriton verrucosus (Caudata: Salamandridae) in Darjeeling

2011 ◽  
Vol 4 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Ritwik Dasgupta
Keyword(s):  
Frequency Distribution ◽  
Primary Productivity ◽  
Egg Size ◽  
Zooplankton Abundance ◽  
Trophic Conditions ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
High Predation ◽  
Hatchling Size ◽  
Predation Rates

The facts that small hatchlings emerged from small eggs laid under high predation levels prevailing at the lower altitudes of distribution of this species in Darjeeling while larger hatchlings emerged from larger eggs laid under lower levels of predation at higher altitudes, show that predation is not selected for large egg and initial hatchling size in this salamandrid species. Metamorphic size was small under high predation rates because this species relied on crypsis for evading predators. Egg and hatchling size are related inversely to levels of primary productivity and zooplankton abundance in lentic habitats. Hatchling sizes are related positively to egg size and size frequency distribution of zooplankton. Small egg and small hatchling size have been selected for at the lower altitudes of distribution of this salamandrid in Darjeeling because predation rates increased in step with improvement in trophic conditions at the lower altitudes.

Pollen Transfer by Natural Hybrids and Parental Species in an Ipomopsis Hybrid Zone

Evolution ◽  
1998 ◽  
Vol 52 (6) ◽  
pp. 1602 ◽  
Author(s):  
Diane R. Campbell ◽  
Nickolas M. Waser ◽  
Paul G. Wolf
Keyword(s):  
Hybrid Zone ◽  
Parental Species ◽  
Pollen Transfer ◽  
Natural Hybrids

scholarly journals Geochemistry of Umm Rus gold - quartz veins, Central Eastern Desert Egypt. A new contribution

2001 ◽  
Vol 34 (3) ◽  
pp. 1139
Author(s):  
O. A. KAMEL ◽  
M. M. EL MAHALLAWI ◽  
H. M. HELMY
Keyword(s):  
Hybrid Zone ◽  
Eastern Desert ◽  
Quartz Diorite ◽  
Low Grade ◽  
Gold Content ◽  
Strongly Correlated ◽  
Quartz Veins ◽  
Central Eastern Desert ◽  
Pan African ◽  
Gold Bearing

Gold-bearing quartz veins of the Umm Rus area occur at the south-eastern contact of a Precambrian granodiorite cupola within younger gabbros of 573-615 Ma belonging to the Pan African orogenic belt. The rocks are intruded within low-grade metasediments. At such contact, a hybrid zone is developed characterized by the occurrence of quartz diorite which grades into diorite and meta-ferrogabro. A limited number of mineralized quartz veins cut the granodiorite-gabbro complex. Different alteration zones are developed in the vicinity of the quartz veins. The quartz veins have two main trends; NS and N30 E, the latter one is usaually gold-bearing. The mineralized parts of the veins commonly consist of highly sheared and banded smoky quartz, and the gold content depends on the relation with the dykes. The element is strongly correlated with As and Ag, but moderately with Cu. Near to intermediate and basic dykes, the contents of Au, Ag and As are noticably increased

Extreme rainfall-related clutch size variation in the Critically Endangered Raso Lark Alauda razae of the arid Cape Verde islands

2018 ◽  
Vol 29 (2) ◽  
pp. 321-326 ◽  
Author(s):  
M. de L. BROOKE
Keyword(s):  
Population Size ◽  
Clutch Size ◽  
Size Variation ◽  
Extreme Rainfall ◽  
Cape Verde ◽  
Critically Endangered ◽  
Strongly Correlated ◽  
Cape Verde Islands ◽  
Rainy Period ◽  
Island Endemic

SummaryThe Raso Lark Alauda razae is a single island endemic confined to the island of Raso in the Cape Verde islands. It has been studied via short (11–20 day), similarly-timed visits every year from 2001 to 2017. These November/December visits have occurred towards the end of the main rainy period (August–October) in the Cape Verdes. Average clutch size ranged from zero (no nests found) to 3.57 in different years and was strongly correlated with rainfall in the three months preceding the year’s visit, but not with population size, which varied 25-fold during the study period. Since the nomadic pursuit of rain is not an option for the Raso Lark, the species adjusts clutch size according to conditions prevailing on Raso.

scholarly journals Effects of Environmental Conditions and Parental Quality on Inter- and Intraclutch Egg-Size Variation in the Collared Flycatcher (Ficedula Albicollis)

The Auk ◽  
2005 ◽  
Vol 122 (2) ◽  
pp. 509-522 ◽  
Author(s):  
Rita Hargitai ◽  
János Török ◽  
László Tóth ◽  
Gergely Hegyi ◽  
Balázs Rosivall ◽  
...  
Keyword(s):  
Egg Size ◽  
Size Variation ◽  
Laying Date ◽  
Life History Trait ◽  
Ficedula Albicollis ◽  
Collared Flycatcher ◽  
Egg Formation ◽  
Adaptive Explanation ◽  
Breeding Condition

AbstractEgg size is a particularly important life-history trait mediating maternal influences on offspring phenotype. Females can vary their egg-size investment in relation to environmental circumstances, their own breeding condition, and the quality of their mate. Here we analyzed inter- and intraclutch variation in egg size in the Collared Flycatcher (Ficedula albicollis) on the basis of eight years of data. According to our results, mean egg size increased with female condition, but did not differ among young, middle-aged, and old females. The male’s age, body size, and forehead patch size did not influence egg size; thus, we found no evidence for differential investment in egg size in relation to male quality. We found no effect of laying date on egg size when controlling for ambient temperature during the egg formation period, yet temperature had a significant effect on egg size. That result indicates proximate constraints on egg formation. Furthermore, we report on annual differences in intraclutch egg-size variation. Egg size increased within clutches in years with a warm prelaying period; whereas in years when the weather during that period was cold, there was no significant intraclutch trend. Proximate considerations seem to explain the observed patterns of intraclutch egg-size variation; however, we cannot reject the adaptive explanation. Mean egg size and intraclutch egg-size variation were unrelated to clutch size. Therefore, we found no evidence for a trade-off between size and number of eggs within a clutch.

scholarly journals Hybridization and hybrid zone stability between two lizards explained by population genetics and niche quantification

2020 ◽  
Vol 190 (2) ◽  
pp. 757-769
Author(s):  
Imanol Cabaña ◽  
Margarita Chiaraviglio ◽  
Valeria Di Cola ◽  
Antoine Guisan ◽  
Olivier Broennimann ◽  
...  
Keyword(s):  
Hybrid Zone ◽  
Parental Species ◽  
Niche Overlap ◽  
Analysis Framework ◽  
Nuclear Marker ◽  
Lizard Species ◽  
New Models ◽  
Species Evolution ◽  
Main Factors ◽  
The Stability

Abstract Understanding the factors that affect hybridization is an important issue in the study of species evolution. In this work, we analyse the genetic structure of two lizard species, Salvator merianae and Salvator rufescens, at a microscale within a climatic niche analysis framework, to reveal the main factors that contribute to the stability of their hybrid zone. We assess the effect of climate in hybridization by quantifying and decomposing the niche overlap of both species. Using a mitochondrial and a nuclear marker, we find that hybridization is frequent and is not restricted to the sympatric region. The gene flow is mainly from S. rufescens to S. merianae, with introgression into the range of S. merianae. Also, S. merianae would have long been present in the area, while S. rufescens appears to be a recent colonizer. The climate contributes to the population structure of S. merianae, but not to that of S. rufescens. The niches occupied by S. rufescens in the hybrid zone and the non-hybrid zone are similar, while the niches of S. merianae are different. Our results do not fit previous models of hybrid zone stability, suggesting the need to develop new models that consider the evolutionary factors that can differentially affect parental species and hybrids.

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