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"Martin, Paul R"
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Impacts of climate warming on terrestrial ectotherms across latitude
The impact of anthropogenic climate change on terrestrial organisms is often predicted to increase with latitude, in parallel with the rate of warming. Yet the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature change. We integrate empirical fitness curves describing the thermal tolerance of terrestrial insects from around the world with the projected geographic distribution of climate change for the next century to estimate the direct impact of warming on insect fitness across latitude. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Available thermal tolerance data for several vertebrate taxa exhibit similar patterns, suggesting that these results are general for terrestrial ectotherms. Our analyses imply that, in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest.
Journal Article
Low Chicago : a Wild cards mosaic novel
\"In George R.R. Martin's latest Wild Cards adventure, a gang of criminals are scattered across time and threaten the stability of the world. Perfect for current fans and new readers alike, Low Chicago is an all-new time travel adventure that leads to the criminal underworld of 1920s Chicago, featuring a fresh cast of characters from the Wild Cards universe.\"-- Provided by publisher.
Book
When David Beats Goliath: The Advantage of Large Size in Interspecific Aggressive Contests Declines over Evolutionary Time
Body size has long been recognized to play a key role in shaping species interactions. For example, while small species thrive in a diversity of environments, they typically lose aggressive contests for resources with larger species. However, numerous examples exist of smaller species dominating larger species during aggressive interactions, suggesting that the evolution of traits can allow species to overcome the competitive disadvantage of small size. If these traits accumulate as lineages diverge, then the advantage of large size in interspecific aggressive interactions should decline with increased evolutionary distance. We tested this hypothesis using data on the outcomes of 23,362 aggressive interactions among 246 bird species pairs involving vultures at carcasses, hummingbirds at nectar sources, and antbirds and woodcreepers at army ant swarms. We found the advantage of large size declined as species became more evolutionarily divergent, and smaller species were more likely to dominate aggressive contests when interacting with more distantly-related species. These results appear to be caused by both the evolution of traits in smaller species that enhanced their abilities in aggressive contests, and the evolution of traits in larger species that were adaptive for other functions, but compromised their abilities to compete aggressively. Specific traits that may provide advantages to small species in aggressive interactions included well-developed leg musculature and talons, enhanced flight acceleration and maneuverability, novel fighting behaviors, and traits associated with aggression, such as testosterone and muscle development. Traits that may have hindered larger species in aggressive interactions included the evolution of morphologies for tree trunk foraging that compromised performance in aggressive contests away from trunks, and the evolution of migration. Overall, our results suggest that fundamental trade-offs, such as those associated with body size, are more likely to break down over evolutionary time, changing the rules that govern species interactions and structure ecological communities.
Journal Article
Knaves over queens
As the alien Xenovirus reaches Britain, Prime Minister Sir Winston Churchill, now gifted with extraordinary longevity, joins with Alan Turing to set up a special organization, the Order of the Silver Helix, to outmaneuver the terrifying mutations of the virus in Britain.
BOOK
Aggressive signaling among competing species of birds
Aggressive interactions help individuals to gain access to and defend resources, but they can be costly, leading to increased predation risk, injury, or death. Signals involving sounds and color can allow birds to avoid the costs of intraspecific aggressive encounters, but we know less about agonistic signaling between species, where fights can be frequent and just as costly. Here, we review photographic and video evidence of aggressive interactions among species of birds (
N
= 337 interactions documenting the aggressive signals of 164 different bird species from 120 genera, 50 families, and 24 orders) to document how individuals signal in aggressive encounters among species, and explore whether these visual signals are similar to those used in aggressive encounters with conspecifics. Despite the diversity of birds examined, most aggressively signaling birds displayed weapons (bills, talons, wings) used in fighting and placed these weapons closest to their heterospecific opponent when signaling. Most species oriented their bodies and heads forward with their bills pointing towards their heterospecific opponent, often highlighting their face, throat, mouth, and bill. Many birds also opened their wings and/or tails, increasing their apparent size in displays, consistent with the importance of body size in determining behavioral dominance among species. Aggressive postures were often similar across species and taxonomic families. Exceptions included Accipitridae and Falconidae, which often highlighted their talons in the air, Columbidae, which often highlighted their underwings from the side, and Trochilidae, which often hovered upright in the air and pointed their fanned tail downward. Most species highlighted bright carotenoid-based colors in their signals, but highlighted colors varied across species and often involved multiple colors in combination (
e.g
., black, white, and carotenoid-based colors). Finally, birds tended to use the same visual signals in aggressive encounters with heterospecifics that they use in aggressive encounters with conspecifics, suggesting that selection from aggressive interactions may act on the same signaling traits regardless of competitor identity.
Journal Article
Repeated patterns of trait divergence between closely related dominant and subordinate bird species
Ecologically similar species often compete aggressively for shared resources. These interactions are frequently asymmetric, with one species behaviorally dominant to another and excluding it from preferred resources. Despite the potential importance of this type of interference competition as a source of selection, we know little about patterns of trait divergence between dominant and subordinate species. We compiled published data on phylogenetically independent, closely related species of North American birds where one species was consistently dominant in aggressive interactions with a congeneric species. We then compared the body size, breeding phenology, life history, ecological breadth, and biogeography of these species. After accounting for body size and phylogeny, we found repeated patterns of trait divergence between subordinate and dominant species within genera. Subordinate species that migrated seasonally arrived 4-7 days later than dominants on their sympatric breeding grounds, and both resident and migratory subordinates initiated breeding 7-8 days later than their dominant, sympatric congeners. Subordinate species had a 5.2% higher annual adult mortality rate and laid eggs that were 0.02 g heavier for their body mass. Dominant and subordinate species used a similar number of different foods, foraging behaviors, nest sites, and habitats, but subordinates were more specialized in their foraging behaviors compared with closely related dominant species. The breeding and wintering ranges of subordinate species were 571 km farther apart than the ranges of dominant species, suggesting that subordinate species migrate greater distances. Range sizes and latitudinal distributions did not consistently differ, although subordinate species tended to breed farther north or winter farther south. These results are consistent with dominant species directly influencing the ecological strategies of subordinate species (via plastic or genetically based changes), either by restricting their access to resources or simply through aggression. Alternatively, these ecological traits may covary with patterns of behavioral dominance, with no direct consequences of interactions. Regardless of the mechanism, recognizing that the relative position of a species within a dominance hierarchy is correlated with a suite of other ecological and fitness related traits has far-reaching implications for the mechanisms underlying species distributions and the structure of biological assemblages.
Journal Article
Retinal ganglion cells projecting to superior colliculus and pulvinar in marmoset
We determined the retinal ganglion cell types projecting to the medial subdivision of inferior pulvinar (PIm) and the superior colliculus (SC) in the common marmoset monkey, Callithrix jacchus. Adult marmosets received a bidirectional tracer cocktail into the PIm (conjugated to Alexa fluor 488), and the SC (conjugated to Alexa fluor 594) using an MRI-guided approach. One SC injection included the pretectum. The large majority of retrogradely labelled cells were obtained from SC injections, with only a small proportion obtained after PIm injections. Retrogradely labelled cells were injected intracellularly in vitro using lipophilic dyes (DiI, DiO). The SC and PIm both received input from a variety of ganglion cell types. Input to the PIm was dominated by broad thorny (41%), narrow thorny (24%) and large bistratified (25%) ganglion cells. Input to the SC was dominated by parasol (37%), broad thorny (24%) and narrow thorny (17%) cells. Midget ganglion cells (which make up the large majority of primate retinal ganglion cells) and small bistratified (blue-ON/yellow OFF) cells were never observed to project to SC or PIm. Small numbers of other wide-field ganglion cell types were also encountered. Giant sparse (presumed melanopsin-expressing) cells were only seen following the tracer injection which included the pretectum. We note that despite the location of pulvinar complex in dorsal thalamus, and its increased size and functional importance in primate evolution, the retinal projections to pulvinar have more in common with SC projections than they do with projections to the dorsal lateral geniculate nucleus.
Journal Article
Variation in the Structure of Bird Nests between Northern Manitoba and Southeastern Ontario
Traits that converge in appearance under similar environmental conditions among phylogenetically independent lineages are thought to represent adaptations to local environments. We tested for convergence in nest morphology and composition of birds breeding in two ecologically different locations in Canada: Churchill in northern Manitoba and Elgin in southeastern Ontario. We examined nests from four families of passerine birds (Turdidae: Turdus, Parulidae: Dendroica, Emberizidae: Passerculus and Fringillidae: Carduelis) where closely related populations or species breed in both locations. Nests of American Robins, Yellow Warblers, and Carduelis finches had heavier nest masses, and tended to have thicker nest-walls, in northern Manitoba compared with conspecifics or congenerics breeding in southeastern Ontario. Together, all species showed evidence for wider internal and external nest-cup diameters in northern Manitoba, while individual species showed varying patterns for internal nest-cup and external nest depths. American Robins, Yellow Warblers, and Carduelis finches in northern Manitoba achieved heavier nest masses in different ways. American Robins increased all materials in similar proportions, and Yellow Warblers and Common Redpolls used greater amounts of select materials. While changes in nest composition vary uniquely for each species, the pattern of larger nests in northern Manitoba compared to southeastern Ontario in three of our four phylogenetically-independent comparisons suggests that birds are adapting to similar selective pressures between locations.
Journal Article
Behavioral dominance interactions between two species of burying beetles ( Nicrophorus orbicollis and Nicrophorus pustulatus )
Closely related species with ecological similarity often aggressively compete for a common, limited resource. This competition is usually asymmetric and results in one species being behaviorally dominant over the other. Trade-offs between traits for behavioral dominance and alternative strategies can result in different methods of resource acquisition between the dominant and subordinate species, with important consequences for resource partitioning and community structure. Body size is a key trait thought to commonly determine behavioral dominance. Priority effects (
i.e
., which species arrives at the resource first), however, can also determine the outcome of interactions, as can species-specific traits besides size that give an advantage in aggressive contests (
e.g
., weapons). Here, we test among these three alternative hypotheses of body size, priority effects, and species identity for what determines the outcome of competitive interactions among two species of burying beetles,
Nicrophorus orbicollis
and
N. pustulatus
. Both overlap in habitat and seasonality and exhibit aggressive competition over a shared breeding resource of small vertebrate carrion. In trials, we simulated what would happen upon the beetles’ discovery of a carcass in nature by placing a carcass and one beetle of each species in a container and observing interactions over 13 h trials (
n
= 17 trials). We recorded and categorized interactions between beetles and the duration each individual spent in contact with the carcass (the key resource) to determine which hypothesis predicted trial outcomes. Body size was our only significant predictor; the largest species won most aggressive interactions and spent more time in contact with the carcass. Our results offer insight into the ecology and patterns of resource partitioning of
N. orbicollis
and
N. pustulatus
, the latter of which is unique among local
Nicrophorus
for being a canopy specialist.
N. pustulatus
is also unique among all
Nicrophorus
in using snake eggs, in addition to other carrion, as a breeding resource. Our results highlight the importance of body size and related trade-offs in ecology and suggest parallels with other coexisting species and communities.
Journal Article