scholarly journals Shifting Paradigms in the Mechanics of Nectar Extraction and Hummingbird Bill Morphology

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
A Rico-Guevara ◽  
M A Rubega ◽  
K J Hurme ◽  
R Dudley
Keyword(s):  
Capillary Rise ◽  
Interference Competition ◽  
Foraging Strategies ◽  
Sexually Dimorphic ◽  
Evolutionary Patterns ◽  
Ulterior Motive ◽  
Ecological Patterns ◽  
Bill Morphology ◽  
Selective Forces ◽  
Adaptive Consequences

Abstract As functional morphologists, we aim to connect structures, mechanisms, and emergent higher-scale phenomena (e.g., behavior), with the ulterior motive of addressing evolutionary patterns. The fit between flowers and hummingbird bills has long been used as an example of impressive co-evolution, and hence hummingbirds’ foraging behavior and ecological associations have been the subject of intense study. To date, models of hummingbird foraging have been based on the almost two-centuries-old assumption that capillary rise loads nectar into hummingbird tongue grooves. Furthermore, the role of the bill in the drinking process has been overlooked, instead considering it as the mere vehicle with which to traverse the corolla and access the nectar chamber. As a scientific community, we have been making incorrect assumptions about the basic aspects of how hummingbirds extract nectar from flowers. In this article, we summarize recent advances on drinking biomechanics, morphological and ecological patterns, and selective forces involved in the shaping of the hummingbird feeding apparatus, and also address its modifications in a previously unexpected context, namely conspecific and heterospecific fighting. We explore questions such as: how do the mechanics of feeding define the limits and adaptive consequences of foraging behaviors? Which are the selective forces that drive bill and tongue shape, and associated sexually dimorphic traits? And finally, what are the proximate and ultimate causes of their foraging strategies, including exploitative and interference competition? Increasing our knowledge of morphology, mechanics, and diversity of hummingbird feeding structures will have implications for understanding the ecology and evolution of these remarkable animals.

Is body shape of mangrove-dwelling monitor lizards (Varanus indicus; Varanidae) sexually dimorphic?

2011 ◽  
Vol 32 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Jan Hnízdo ◽  
Veronika Cikánová ◽  
Olga Šimková ◽  
Daniel Frynta ◽  
Petr Velenský ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Body Shape ◽  
Sexually Dimorphic ◽  
Evolutionary Explanation ◽  
Body Measurements ◽  
Male And Female ◽  
Fecundity Selection ◽  
Selective Forces ◽  
Monitor Lizards

AbstractIn monitor lizards, males are typically larger than conspecific females, but body shape is usually quite similar in both sexes. This not only represents a puzzle worthy of evolutionary explanation, but also makes field sex determination of monitor lizards difficult. We asked whether subtle differences in body shape follow the same pattern as in other sexually dimorphic lizard taxa and thus can be explained by the same selective forces. We tested the hypotheses that (1) females have a longer abdomen due to fecundity selection and (2) males possess bigger heads due to intrasexual selection. We also hypothesised that (3) male monitors show a wider chests and longer upper fore-limbs to win male-male wrestling matches. We monitored ontogeny in 35 mangrove-dwelling monitors (Varanus indicus). Seventeen body measurements were taken every three months up to the age of 24-34 months. Sex was determined by an ultrasonographic imaging. We employed multiple approaches to remove the effect of size and used both confirmation and exploratory statistics. The results revealed that sexual differences in body shape were small and emerged after maturity. Females have a relatively longer abdomen while males wider chest and longer upper fore-limbs. Thus, the differences in body shape between male and female varanid lizards may be attributed to both fecundity and sexual selection.

Male and female pups of the highly sexually dimorphic northern elephant seal (Mirounga angustirostris) differ slightly in body size

2019 ◽  
Vol 97 (3) ◽  
pp. 241-250
Author(s):  
E. Salogni ◽  
F. Galimberti ◽  
S. Sanvito ◽  
E.H. Miller
Keyword(s):  
Body Size ◽  
Early Life ◽  
Sexual Size Dimorphism ◽  
Elephant Seal ◽  
Sexually Dimorphic ◽  
Mirounga Angustirostris ◽  
Northern Elephant Seal ◽  
Size Dimorphism ◽  
Selective Forces ◽  
Size At Birth

In mammals, males generally are larger than females, though such sexual-size differences have been documented primarily in adults and are relatively poorly known in early life. We studied sexual-size differences in pups of the northern elephant seal (Mirounga angustirostris (Gill, 1866)), which in adulthood is one of the most sexually dimorphic mammals. We studied body size at birth and weaning, at Islas San Benito, Mexico, at the southernmost limit of the species’ breeding range. Males were 10% heavier and 2% longer than females at birth. Sexes did not differ significantly in either measure of body size at weaning, although males were slightly heavier (4%) and longer (1%) than females. Neither growth rate nor suckling duration differed between the sexes. In previous studies in California, USA, pups at weaning were heavier than in our study, and males were heavier than females. These differences may reflect ecological, temporal, or life-history differences across populations. The modest difference in sexual-size dimorphism early in life in this species compared with the great difference in adulthood likely reflects multiple selective forces, including constraints on neonatal size set by body size of females, and the weakness of sexual selection at that stage of life.

scholarly journals Diversification through sexual selection on gustatorial courtship traits in dwarf spiders

2021 ◽  
Author(s):  
Shou-Wang Lin ◽  
Gabriele Uhl ◽  
Lara Lopardo
Keyword(s):  
Sexual Selection ◽  
Anterior Part ◽  
Ecological Factors ◽  
Sexually Dimorphic ◽  
Ancestral State ◽  
Evolutionary Patterns ◽  
Character Matrix ◽  
High Lability ◽  
Secretory Glands

Sexual dimorphism can evolve under sexual selection or ecological factors. Sexually dimorphic male prosomal modifications are associated with gustatorial courtship in erigonines. The modifications vary from moderate elevations to bizarre shapes. Males transfer substances from these structures to females, which affect mate acceptance and fecundity. Here, we explore lability of these traits by investigating if modified prosomata are inherently linked to secretory glands, if glands evolved prior to prosomal modifications, and the possibility of convergent evolution and cryptic differentiation, aiming at assessing the possible role of this trait complex in speciation. We reconstructed the positions of glands and the musculature in the anterior part of prosomata of 76 erigonines and three outgroups using micro-CT. We incorporated these characters into an existing morphological character matrix and reanalyzed the phylogeny. Our results support the possession of glands as the ancestral state. The manifold modifications of the prosomal shape have evolved convergently. Differences in glandular positions between species with modified/unmodified prosomata suggest high lability of these traits. Cases of gland loss suggest considerable costs of gustatorial courtship. Our findings demonstrate divergent evolutionary patterns of these traits, and a likely facilitating effect of this type of sexual selection on speciation.

scholarly journals Diversification Through Gustatorial-Courtship: An X-ray Micro-Computed Tomography Study on Dwarf Spiders

2021 ◽  
Author(s):  
Shou-Wang Lin ◽  
Lara Lopardo ◽  
Gabriele Uhl
Keyword(s):  
Computed Tomography ◽  
Sexual Selection ◽  
Anterior Part ◽  
Sexually Dimorphic ◽  
Ancestral State ◽  
Glandular Tissue ◽  
Micro Computed Tomography ◽  
Evolutionary Patterns ◽  
X Ray ◽  
Outgroup Species

Abstract BackgroundSexual selection has been considered to promote diversification and speciation. Sexually dimorphic species have been used to explore the supposed effect, however, with mixed results. In dwarf spiders (Erigoninae), many species are sexually dimorphic - males possess marked prosomal modifications. These male traits vary from moderate elevation to bizarre shapes in various prosomal regions. Previous studies established that male dwarf spiders produce substances in these prosomal modifications that are taken up by the female. Since the transfer of substances increases mating probability of males and oviposition rate in females, the dimorphic traits evolved in the context of sexual selection. Here, we explore the evolutionary lability of the gustatory trait complex by investigating 1) if erigonine modified prosomata are inherently linked to nuptial-gift-producing glands, 2) if gland evolution preceded that of the modified prosomal shapes and by assessing 3) the probability of convergent evolution and cryptic differentiation - with the aim of assessing the role of this trait complex in species divergence.ResultsWe reconstructed the position and extent of the glandular tissue along with the muscular anatomy in the anterior part of the prosoma of 76 erigonine spiders and three outgroup species using X-ray micro-computed tomography. We incorporated the location of glands and muscles into an existing matrix of somatic and genitalic morphological traits of these taxa and reanalyzed their phylogenetic relationship. Our analysis supports that possession of glandular equipment is the ancestral state. The manifold modifications of the prosomal shape have evolved convergently multiple times. We found differences in glandular position between species with both modified and unmodified prosomata, and reported on seven cases of gland loss. ConclusionsOur findings suggest that the occurrence of gustatory gland in sexually monomorphic ancestors has set the stage for the evolution of diverse dimorphic external modifications in dwarf spiders. Variation among congeners indicates that glandular position is highly susceptible to changes. Multiple incidences of gland loss suggest considerable maintenance costs of glandular tissue and nuptial feeding. Our results demonstrate divergent evolutionary patterns of gustatorial-courtship-related traits, and a likely facilitating effect of this type of sexual selection on speciation

scholarly journals Avian diet and foraging ecology constrain foreign egg recognition and rejection

2020 ◽  
Vol 13 (1-2) ◽  
pp. 24-31
Author(s):  
Alec B Luro ◽  
Mark E Hauber
Keyword(s):  
Host Species ◽  
Brood Parasitism ◽  
Foraging Ecology ◽  
Foraging Strategies ◽  
Egg Rejection ◽  
Egg Recognition ◽  
Body Sizes ◽  
Bill Morphology ◽  
Avian Brood Parasitism ◽  
Rejection Rates

Egg rejection is a common and effective defense against avian brood parasitism in which the host either marginalizes or removes the parasitic egg or deserts the parasitized clutch. The ability to recognize and reject a parasitic egg depends on bill morphology, sensory systems, and cognition, all of which are also shaped by other selective processes such as foraging. This begs the question whether specific phenotypes associated with different foraging strategies and diets may constrain or facilitate egg recognition and rejection. Here, we propose a novel hypothesis that host species phenotypes related to foraging ecology and diet may impose morphological and visual sensory constraints on the evolution of egg recognition and rejection. We conducted a comparative analysis of the adult diets and egg rejection rates of 165 current host and non-host species. We found that species have significantly higher egg rejection rates when they (1) consume an omnivorous or animal and fruit dominated diet rather than seeds and grains, (2) forage arboreally rather than aerially or on the ground, or (3) possess relatively larger body sizes. Although correlational in nature, as predicted, these results suggest phenotypes related to specific diets and foraging ecologies may differentially constrain or facilitate evolution of host egg rejection defenses against avian brood parasitism.

Interference competition in a sexually dimorphic shorebird: prey behaviour explains intraspecific competition

2014 ◽  
Vol 92 ◽  
pp. 195-201 ◽  
Author(s):  
Sjoerd Duijns ◽  
Theunis Piersma
Keyword(s):  
Intraspecific Competition ◽  
Interference Competition ◽  
Sexually Dimorphic

scholarly journals The evolution of derived monomorphism from sexual dimorphism: A case study on salamanders

2020 ◽  
Author(s):  
Nancy L Staub
Keyword(s):  
Sexual Dimorphism ◽  
The Other ◽  
Head Width ◽  
Social Selection ◽  
Sexually Dimorphic ◽  
Ecological Significance ◽  
Selective Forces ◽  
Males And Females ◽  
Shed Light

Abstract While sexual dimorphism has long received special attention from biologists, derived monomorphism, the condition in which both males and females express similar derived features, has been less well studied. Historically, the appearance of “male-like” features in females has been explained by the genetic correlation between the sexes. Recent work emphasizes the importance of studying the independent selective forces on both females and males to understand sexual dimorphism. Sexual dimorphism and derived monomorphism in the genus Aneides are examined in light of predictions of social selection. Aneides hardii shows the greatest degree of sexual dimorphism in snout-vent length and head width, with the other species of Aneides less sexually dimorphic. This reduced dimorphism, however, is not a return to an ancestral monomorphic state, but rather exemplifies derived monomorphism because females express traits that were limited in expression to males of ancestral species. Instead of calling these “male-typical” traits in females, I suggest the term “derived monomorphic” traits, as these traits are typical in these females and “derived monomorphic” can apply to both sexes. Increased attention to studying the patterns and ecological significance of derived monomorphism will shed light on the underlying selective forces, including sexual selection, on both females and males.

Assessing the effects of fish density, habitat complexity, and current velocity on interference competition between bull trout (Salvelinus confluentus) and brook trout (Salvelinus fontinalis) in an artificial stream

2013 ◽  
Vol 91 (9) ◽  
pp. 619-625 ◽  
Author(s):  
Will G. Warnock ◽  
Joseph B. Rasmussen
Keyword(s):  
Current Velocity ◽  
Brook Trout ◽  
Habitat Complexity ◽  
Salvelinus Fontinalis ◽  
Interference Competition ◽  
Foraging Strategies ◽  
Fish Density ◽  
Stream Velocity ◽  
Bull Trout ◽  
Salvelinus Confluentus

In this experiment, competition was observed among native bull trout (Salvelinus confluentus (Suckley, 1859)) and non-native brook trout (Salvelinus fontinalis (Mitchill, 1814)) in artificial streams. In intraspecific competitions, brook trout engaged in territorial interference foraging strategies, and their foraging success was correlated with occupancy of the lead position in the stream. No correlation was apparent for bull trout, most of which engaged in nonterritorial scramble foraging tactics. In interspecific competitions, four stream environments were constructed in which fish density, habitat complexity, and current velocity were altered. Bull trout outcompeted brook trout for food in simple pool habitat devoid of cover when competition was head-to-head (density = 3 fish·m−2) between the species. When competitor number was doubled in this habitat, the two became equal competitors. At this higher density, bull trout again outcompeted brook trout for food when the habitat was changed to a complex riffle with substrate cover. Brook trout were more aggressive towards bull trout than vice versa, and interspecific aggression was decreased by low density, cover, and high stream velocity. Territorial brook trout aggressively interfere with their competitor for access to resources, but the success and intensity of this tactic against bull trout may be mitigated by environmental factors.

scholarly journals Digit ratio in three species of tropidurid lizards

Herpetozoa ◽  
2021 ◽  
Vol 34 ◽  
pp. 67-70
Author(s):  
Kelton Gonçalves Miranda ◽  
Marcella Junqueira Goulart ◽  
Conrado Barbosa Galdino
Keyword(s):  
Sexual Dimorphism ◽  
Sex Hormones ◽  
Digit Ratio ◽  
Sexually Dimorphic ◽  
Lizard Species ◽  
Finger Length ◽  
Digit Ratios ◽  
Selective Forces ◽  
Males And Females ◽  
Interpopulation Variation

Proportions between pairs of digits are linked to fitness in tetrapods and they can be influenced by sex hormones through individuals’ ontogenies. Therefore, in many species, the proportions amongst finger length ratios (referred as digit ratio, i.e. 2D second and 4D fourth digits) can differ between males and females. We investigated whether the three most commonly used forelimb digit ratios are sexually dimorphic in three tropidurid species. In one of the three lizard species, Eurolophosaurus nanuzae, males and females differ for only 2D:4D digit ratio. Otherwise, our results on the studied Tropidurus species conform to previous studies showing no differences in digit ratios between males and females. Hence, it might be the case of local selective forces shaping interpopulation variation in the expression of sexual dimorphism for digit ratio.

scholarly journals Sexual Mismatch Between Vessel-Associated Foraging and Discard Consumption in a Marine Top Predator

2021 ◽  
Vol 8 ◽  
Author(s):  
Joan Giménez ◽  
Gavin E. Arneill ◽  
Ashley Bennison ◽  
Enrico Pirotta ◽  
Hans D. Gerritsen ◽  
...  
Keyword(s):  
Sex Differences ◽  
Foraging Behaviour ◽  
Foraging Strategies ◽  
Ecological Niches ◽  
Sexually Dimorphic ◽  
Fishing Vessels ◽  
Cost Of Locomotion ◽  
The Cost ◽  
Dimorphic Species ◽  
Insight Into

Sex differences in diet and foraging behaviour are common in sexually dimorphic species, often driven by differences in the cost of locomotion or ability to exploit different ecological niches. However, sex-specific foraging strategies also occur in monomorphic or slightly dimorphic species where the drivers are poorly understood. Here, we study sex differences in foraging of northern gannets (Morus bassanus), where females are only slightly heavier than males. Using concurrently tracked gannets (298 full foraging trips from 81 individuals) and fishing vessels across 5 years, we quantify individual-based vessel-associated putative foraging, and relate this to discard consumption. We found a significant positive relationship between time spent in vessel-associated foraging and discard consumption for both sexes. However, while females showed greater proportions of vessel-associated foraging than males, discarded fish contributed less to the diet of females in all years. These results contrast with previous suggestions that female gannets interact with vessels less often than males, and are consistent with competitive exclusion of females from trawler-associated discards. Our findings give insight into sexual differences in foraging behaviour in the absence of dimorphism that are necessary to predict their response to environmental and anthropogenic changes.

Sign in / Sign up

Export Citation Format

Share Document