Coming to America: Acclimation in macaque body structures and Bergmann’s rule

I analyzed somatometric measurements from subsets of the Texas and Oregon transplanted troops of Japanese macaques(Macaca fuscata) to reveal secular changes in body size and shape. Body weights of the Texas population (N = 59) are lower than those of the Oregon population(N = 49) and the founding population from Arashiyama. The adult weights of the Oregon population are significantly higher than the founding population from Mihara. There are significant differences in adult circumferential measures and in skinfolds, which are correlated with the increased weight of the Oregon macaques. The adult Texas macaques have longer limb segments in comparison with the adult Oregon troop members, while the latter have significantly longer heads and trunks. Examination of the developing morphological trends through regression analyses on the complete sample suggests distinctive growth patterns for each population. Members of the Texas population start with smaller initial measurements but hold a steeper growth pattern for limb segments, while the Oregon macaques start larger in most measures and show lower growth rates. I argue that these differences in both somatometry and growth patterns are related to the differing climatic conditions under which the translocated macaques have lived. This set of analyses supports the basic arguments for Bergmann’s rule and Allen’s rule.     

Declining body size: a third universal response to warming?

A recently documented correlate of anthropogenic climate change involves reductions in body size, the nature and scale of the pattern leading to suggestions of a third universal response to climate warming. Because body size affects thermoregulation and energetics, changing body size has implications for resilience in the face of climate change. A review of recent studies shows heterogeneity in the magnitude and direction of size responses, exposing a need for large-scale phylogenetically controlled comparative analyses of temporal size change. Integrative analyses of museum data combined with new theoretical models of size-dependent thermoregulatory and metabolic responses will increase both understanding of the underlying mechanisms and physiological consequences of size shifts and, therefore, the ability to predict the sensitivities of species to climate change.     

Avian body size changes and climate change: warming or increasing variability?

There has been a growing interest in whether established ecogeographical patterns, such as Bergmann's rule, explain changes in animal morphology related to climate change. Bergmann's rule has often been used to predict that body size will decrease as the climate warms, but the predictions about how body size will change are critically dependent on the mechanistic explanation behind the rule. To investigate change in avian body size in western North America, we used two long‐term banding data sets from central California, USA; the data spanned 40 years (1971–2010) at one site and 27 years (1983–2009) at the other. We found that wing length of birds captured at both sites has been steadily increasing at a rate of 0.024–0.084% per year. Although changes in body mass were not always significant, when they were, the trend was positive and the magnitudes of significant trends were similar to those for wing length (0.040–0.112% per year). There was no clear difference between the rates of change of long‐distance vs. short‐distance migrants or between birds that bred locally compared to those that bred to the north of the sites. Previous studies from other regions of the world have documented decreases in avian body size and have used Bergmann's rule and increases in mean temperature to explain these shifts. Because our results do not support this pattern, we propose that rather than responding to increasing mean temperatures, avian body size in central California may be influenced by changing climatic variability or changes in primary productivity. More information on regional variation in the rates of avian body size change will be needed to test these hypotheses.     

Relationships between abundance and body size: where do tourists fit?

Abstract.

• 1 The possible effects of the inclusion of ‘tourist’ species have been the cause of some concern in investigations of interspecific relationships between abundance and body size.
• 2 Data for adult beetles (Coleoptera) from oak trees in Britain are used to investigate the relationship of abundance to body size when tourists are and are not included.
• 3 For this particular assemblage, tourists do not fundamentally alter the basic statistics of the relationship between abundance and body size. However, they are not a random sample of the beetle assemblage. They have lower abundances and are also of smaller body size than other species.

     

Scaling of species diversity and body mass in mammals: Cope’s rule and the evolutionary cost of large size

Abstract

Equations are constructed describing the inverse correlation of species diversity and body mass in extant and Cenozoic mammals. Cope’s rule, the tendency for many mammal clades to increase in body size through time, through phyletic change in single lineages or turnover within species groups, is interpreted as a probability function reducing diversity potential as a tradeoff for ecological/evolutionary gains. The inverse rule predicts that large species in clades will be less diverse than smaller species and, unless origination rates remain high among smaller clade members, clades conforming to Cope’s rule will decline in diversity, moving towards extinction. This proposition is evaluated in the Cenozoic histories of five North American mammal clades; cotton rats, felids, canids, hyaenodontids, and equids. Diversity potential of different size classes within the 3.75 million year phyletic history of the muskrat, Ondatra zibethicus, is also examined. A corollary prediction of the inverse rule, that large species should have longer durations (species lifespans) than small species, is unresolved. Successful clades maintain small size or a significant number of smaller species relative to clade average size. The potential loss of unique extant large mammal species justifies the conservation effort to protect them. The similarity of scaling exponents of species diversity to mass around a slope of -1.0 suggests that species diversity is correlated with home range size, the latter related to the probability of population fragmentation.     

The balance between predictions and evidence and the search for universal macroecological patterns: taking Bergmann’s rule back to its endothermic origin

Geographical variation in environmental temperatures is expected to impose clinal phenotypic selection that results in the expression of large-scale gradients of body mass variation within animal clades. Body size is predicted to increase with increasing latitude and elevation, and hence, with decreasing temperature, a pattern broadly known as Bergmann’s rule. However, empirical observations are highly conflicting. Whilst most studies support this prediction in endotherms (birds and mammals), analyses conducted on ectotherms often fail to report this pattern. Does it reduce the validity of this macroecological rule? Since the original formulation of Bergmann’s rule only involved endothermic organisms, I argue that the controversy is not a consequence of its predictive power, but a result of the later inclusion of ectotherms as part of the prediction. Here, I propose that the common conception of Bergmann’s rule maintained for half a century is changed back to its original definition restricted to endotherms. This temperature–size relationship might therefore consolidate as a well-established macroecological rule if its original formulation is respected. Finally, I develop these claims on my initial suggestion that Bergmann’s rule should be recognized as the evolutionary outcome of a general process with no phylogenetic scale distinction of species or populations, being equally applicable amongst and within species.     

Shrinking body sizes in response to warming: explanations for the temperature–size rule with special emphasis on the role of oxygen

Body size is central to ecology at levels ranging from organismal fecundity to the functioning of communities and ecosystems. Understanding temperature-induced variations in body size is therefore of fundamental and applied interest, yet thermal responses of body size remain poorly understood. Temperature–size (T–S) responses tend to be negative (e.g. smaller body size at maturity when reared under warmer conditions), which has been termed the temperature–size rule (TSR). Explanations emphasize either physiological mechanisms (e.g. limitation of oxygen or other resources and temperature-dependent resource allocation) or the adaptive value of either a large body size (e.g. to increase fecundity) or a short development time (e.g. in response to increased mortality in warm conditions). Oxygen limitation could act as a proximate factor, but we suggest it more likely constitutes a selective pressure to reduce body size in the warm: risks of oxygen limitation will be reduced as a consequence of evolution eliminating genotypes more prone to oxygen limitation. Thus, T–S responses can be explained by the ‘Ghost of Oxygen-limitation Past’, whereby the resulting (evolved) T–S responses safeguard sufficient oxygen provisioning under warmer conditions, reflecting the balance between oxygen supply and demands experienced by ancestors. T–S responses vary considerably across species, but some of this variation is predictable. Body-size reductions with warming are stronger in aquatic taxa than in terrestrial taxa. We discuss whether larger aquatic taxa may especially face greater risks of oxygen limitation as they grow, which may be manifested at the cellular level, the level of the gills and the whole-organism level. In contrast to aquatic species, terrestrial ectotherms may be less prone to oxygen limitation and prioritize early maturity over large size, likely because overwintering is more challenging, with concomitant stronger end-of season time constraints. Mechanisms related to time constraints and oxygen limitation are not mutually exclusive explanations for the TSR. Rather, these and other mechanisms may operate in tandem. But their relative importance may vary depending on the ecology and physiology of the species in question, explaining not only the general tendency of negative T–S responses but also variation in T–S responses among animals differing in mode of respiration (e.g. water breathers versus air breathers), genome size, voltinism and thermally associated behaviour (e.g. heliotherms).     

Body size and elevation: do Bergmann's and Rensch's rule apply in the polytypic bushcricket Poecilimon veluchianus?

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Cope's rule in cryptodiran turtles: do the body sizes of extant species reflect a trend of phyletic size increase?

Cope's rule of phyletic size increase is questioned as a general pattern of body size evolution. Most studies of Cope's rule have examined trends in the paleontological record. However, neontological approaches are now possible due to the development of model-based comparative methods, as well as the availability of an abundance of phylogenetic data. I examined whether the phylogenetic distribution of body sizes in extant cryptodiran turtles is consistent with Cope's rule. To do this, I examined body size evolution in each of six major clades of cryptodiran turtles and also across the whole tree of cryptodirans (n = 201 taxa). Extant cryptodiran turtles do not appear to follow Cope's rule, as no clade showed a significant phyletic body size trend. Previous analyses in other extant vertebrates have also found no evidence for phyletic size increase, which is in contrast to the paleontological data that support the rule in a number of extinct vertebrate taxa.     

Acid-mediated Lipinski’s second rule: application to drug design and targeting in cancer

With a predicted 382.4 per 100,000 people expected to suffer from some form of malignant neoplasm by 2015, and a current death toll of 1 out of 8 deaths worldwide, improving treatment and/or drug design is an essential focus of cancer research. Multi-drug resistance is the leading cause of chemotherapeutic failure, and delivery of anticancer drugs to the inside of cancerous cells is another major challenge. Fifteen years ago, in a completely different field in which improving drug delivery is the objective, the bioavailability of oral compounds, Christopher Lipinski formulated some rules that are still used by the pharmaceutical industry as rules of thumb to improve drug delivery to their target. Although Lipinski’s rules were not formulated to improve delivery of antineoplastic drugs to the inside of cancer cells, it is interesting to note that the problems are similar. On the basis of the strong similarity between the fields, we discuss how they can be connected and how new drug targets can be defined in cancer.     

Me against who? Male guppies adjust mating behaviour according to their rival’s presence and attractiveness

Sexual selection theory suggests that males need to constantly reappraise their mating decisions to take account of the presence and the phenotypes of their rivals. Here we examine this expectation by asking: (i) If the presence of a rival influences male mating behaviour; (ii) How important is the attractiveness of the rival (absolute attractiveness) in shaping male behaviour; and (iii) How does a male's attractiveness in comparison to his rival (relative attractiveness) influence a male's mating decisions. Using the Trinidadian guppy, a species in which female mate choice (based on males’ attractive traits) plays an important role in male mating outcomes, we recorded the frequency of courtship displays and unsolicited attempts by focal males. First, we quantified focal male mating behaviour with and without a rival. Since the probability of a successful mating is, on average, halved by the presence of a rival, we predicted that under competition the focal male would invest more in less costly mating tactic—unsolicited attempts. Second, we examined how the rival's standard length and area of orange coloration mediated focal male mating behaviour. We found that rival presence influenced how focal males responded to females in terms of both mating tactics. However, the rival attractiveness elicited changes only in male courtship display. Focal males increased courtship display rate if his rival was small or if possessed large amounts of orange, regardless of considering rival absolute or relative attractiveness. Our results show that males invest in the costlier mating tactic when there is no rival or in the presence of a smaller rival. Interestingly, they make a similar investment in the presence of an attractive orange rival. Overall, this study highlights the importance of fine‐grained male decisions in mating encounters and shows that mating tactics are differentially shaped by multiple competition risk cues.     

Blue tail and striped body: why do lizards change their infant costume when growing up?

Ontogenetic changes in color and pattern that are not directlyrelated to reproduction are very common yet remain a poorlyunderstood phenomenon. One example is conspicuous colors inthe tails of fish, amphibians, and reptiles that fade out laterin life. We suggest a novel hypothesis: conspicuous tail colorsthat appear only in juveniles compensate for an increased activitylevel, deflecting imminent attacks to the tail. We observedblue-tailed, newly hatched lizards (Acanthodactylus beershebensis)in the field and compared 5 behavioral parameters with thoseof older individuals that had already lost their neonate coloration.In addition, we explored whether tail displays, often assumedto direct a predator's attention to the tail, disappear withthe color change. Striped blue-tailed hatchlings foraged moreactively than 3-week-old juveniles, spent a longer time in openmicrohabitats, and performed deflective tail displays. In comparison,2 other lacertids that do not undergo ontogenetic change didnot switch to safer foraging when growing up. The results suggestthat activity alteration may be a major factor affecting theontogenetic color and pattern change. Active lizards that foragein open habitats increase their probability of attack by ambushpredators. Conspicuous colors and deflection displays may shiftattacks to the expendable tail, increasing the prey's overallprobability of surviving attacks. The persistence of both stripedbody pattern and blue tail fits the active foraging period ofneonates and hence may be appropriate for other species thatdisplay a conspicuous tail accompanied by a striped pattern.     

Too short to spawn? Implications of small body size and swimming distance on successful migration and maturation of the European eel Anguilla anguilla

Individual net fat reserves after migration and reproductive investments were calculated for migrating female silver eels Anguilla anguilla (n = 387) collected in the outlet region of the Baltic Sea during the autumn run. It is estimated that 20·4% of the A. anguilla had completely exhausted all initial fat reserves and that 45·0% of A. anguilla were within 90% of complete energy depletion after migration and reproduction. This study concludes that a combination of body size and distance (6900 km) to the spawning area in the Sargasso Sea explains the results. An increase in the costs of migration due to heavy infection with Anguillicoloides crassus was also evaluated in an additional scenario with results showing that 26·4% of the A. anguilla had completely depleted all fat reserves. It is hypothesized that a large proportion of female silver A. anguilla from the Baltic Sea catchment area will have inadequate or suboptimal reserves for successful migration and reproduction.     

Relationships between body size and sound‐producing structures in crickets: do large males have large harps?

Abstract. Male crickets produce conspicuous acoustic signals to attract mates and deter potential rivals. These signals are created when a male cricket closes his wings rapidly and a file and scraper mechanism causes several areas of the wing to vibrate. The harp is an area of the wing that is part of the resonating structure. Because the harp acts as part of a mechanical resonator, changes in harp area or mass could influence the frequency of sound produced. Because females exhibit stabilizing selection on the frequency used in male songs, we hypothesized that there would be a negative allometric relationship between body size and harp area. In addition, we examined the degree of asymmetry in the harp, wing, and tibia. We examined this in four different species of cricket: Acheta domesticus, Gryllus bimaculatus, Gryllus rubens , and Teleogryllus oceanicus. For each species, we measured pronotum width as an index of body size, tibia length, and the area of the forewing and harp. There were significant differences among species in their morphological characteristics. We observed consistent directional asymmetry in the harp area but not in the total wing area. When wings did exhibit directional asymmetry, it was in the opposite direction of the directional asymmetry observed in the harp. Within species, larger males typically had larger harps and the relationship between harp area and body size exhibited negative allometry. Wing area exhibited an isometric relationship with body size. Our data provide a potential mechanism linking decreases in song frequency with body size in male crickets, and suggest that sensory constraints might influence the morphology of signaling structures in a similar fashion as genitalia.     

Ephrin signaling: One raft to rule them all? One raft to sort them? One raft to spread their call and in signaling bind them?

The Eph receptor tyrosine kinases (RTK) and their membrane-bound ligands, the ephrins, mediate cell-contact-dependent signaling events that control multiple aspects of metazoan embryonic development. The ephrins and their receptors regulate cell movement that is essential for forming and stabilizing the spatial organization of tissues and cell types. This includes the guidance of migrating cells or neuronal growth cones to specific targets. Although the biological responses mediated by the ephrin-Eph system were thought to be imparted by the Eph receptor via 'classical' RTK signaling pathways, there is now accumulating evidence that the ephrins are not merely ligands but have biological activity independent of the kinase activity of their cognate Eph receptor. This activity is commonly referred to as 'reverse' or 'bi-directional' signaling. Furthermore, ephrin-mediated signaling is restricted to specific membrane microdomains known as 'lipid rafts', which we believe imparts specificity to the extracellular signal. This review highlights the current data to support a role for lipid rafts in regulating aspects of ephrin-mediated signaling.     

Should ‘wetlands’ cover all aquatic ecosystems and do macrophytes make a difference to their ecosystem services?

The Ramsar Convention has gradually expanded the scope of the term ‘wetland’ to bring under its umbrella all kinds of inland freshwater (and saline) ecosystems as well as many marine ecosystems. It is not possible to develop a common framework for the study, management or policy of such a large and divergent assemblage of habitats with water being a single shared feature. In this paper, I argue that wetlands are distinct from deep open water systems such as rivers, lakes and reservoirs. The restriction of macrophytes (except the free floating plants like salvinia and water hyacinth) to shallow water habitats helps distinguish between wetlands and deep water systems. Following an ecosystem service approach, I discuss that wetlands are generally characterized by the occurrence of macrophytes, which critically contribute to their provisioning, regulating, supporting and cultural ecosystem services that differ significantly from those of the microphyte (phytoplankton)-dominated deep water habitats. I argue that wetlands do lie adjacent to deep and open water systems (including large rivers), which interact with them regularly and influence their biodiversity, hydrology, water quality and functioning, depending upon their relative areal extent and characteristics of the macrophyte community, but that only the littoral zones between the mean highest and lowest water levels (and stream banks and the floodplains beyond them in the case of rivers) should be treated as wetlands. Shallow lakes devoid of macrophytes because of eutrophication are degraded wetlands that need to be restored.     

Trichomes as dangerous lollipops: Do lizards also use caterpillar body and frass odor to optimize their foraging?

When attacked by herbivores, plants produce toxic secondary metabolites that function as direct defenses, as well as indirect defenses that attract and reward predators of the offending herbivores. These indirect defenses include both nutritive rewards such as extra floral nectar, as well as informational rewards, such as the production and release of volatile compounds that betray the location of feeding herbivores to predators. Herbivory of Nicotiana attenuata by the tobacco hornworm (Manduca larvae) alters the volatile profiles of both the plant and larval headspace. Herbivory-elicited specific changes in the volatile profiles are detected by arthropod predators of Manduca larvae. The known predators that perceive volatile cues induced by Manduca herbivory of N. attenuata are insects that target Manduca at early developmental stages, when the larvae are still small; large, late-instar larvae may have outgrown these predation risks. However, here we offer evidence that branched chain aliphatic acids derived from the digestion of plant O-acyl sugars from trichomes may betray Manduca larvae to lizard predators during late developmental stages as well.