Males in many species invest substantially structures that are used combat with rivals over access to females. These weapons can attain extreme proportions and have diversified form repeatedly. I review empirical literature on the function evolution of sexually selected clarify important unanswered questions for future research. Despite their shapes sizes, multitude habitats within which they function, animal share properties: They evolve when males able defend spatially restricted critical...

Truthful Embellishments Exaggerated ornaments such as beetle horns, deer antlers, and extreme tail lengths in birds are typically assumed to be subject sexual selection because they signal the quality of an individual's breeding status—but how? Emlen et al. (p. 860 , published online 26 July) present a general mechanistic model for evolution exaggerated traits, proposing that sensitivity insulin response pathway can explain variation among individuals. The size their increased variability...

Changes in form during ontogeny and evolution depend large measure on changes the relative growth of various parts body. The current consensus developmental biology is that final size appendages internal organs regulated autonomously, within structure itself. Size regulation body typically requires no external control thought to be relatively insensitive signals from environment. We show two very different systems, butterfly wings beetle horns, experimentally induced allocation resources one...

Sexual selection can favor production of extravagant ornaments and weapons in the contest for access to opposite sex. Existing explanations diversity sexually selected structures focus on reproductive benefits conferred by particular ornament or weapon morphologies. Here, I show that costs also may drive patterns evolution. In beetles, horns reduces size neighboring morphological (antennae, eyes, wings, depending location horns), these tradeoffs reveal unexpected functional associations...

It has long been recognized that male mating competition is responsible for the evolution of weaponry mate acquisition. However, when females with more than one male, between males can continue after in form sperm competition. Theory predicts should increase their investment production as increased, but it assumes face a trade-off and other life-history traits such Here, we use genus horned beetle, Onthophagus , to examine testes required fertilizations weapons used obtain matings. In...

Both ornaments and weapons of sexual selection frequently exhibit prolific interspecific diversity form. Yet, most studies this have focused on involved with female mate choice, rather than the male competition. With few exceptions, mechanisms divergence in weapon morphology remain largely unexplored. Here, we characterize evolutionary radiation one type weapon: beetle horns. We use partial sequences from four nuclear three mitochondrial genes to develop a phylogenetic hypothesis for...

Males of the horned beetle Onthophagus acuminatus Har. (Coleoptera: Scarabaeidae) exhibit horn length dimorphism due to a sigmoidal allometric relationship between and body size: steep slope allometry around inflection sigmoid curve separates males into two groups; those larger than this possess long horns, smaller have short horns or lack horns. I examined genetic basis size by selecting that produced unusually for their respective sizes. After seven generations selection, lines selected...

Many scarab beetles produce rigid projections from the body called horns. The exaggerated sizes of these structures and staggering diversity their forms have impressed biologists for centuries. Recent comparative studies using DNA sequence-based phylogenies begun to reconstruct historical patterns beetle horn evolution. At same time, developmental genetic experiments elucidate how horns grow growth is modulated in response environmental variables, such as nutrition. We bring together two...

Darwin considered the horns of male beetles to be among most striking examples sexual selection. As with antlers in deer or elk, beetle scale positively body size, result that large males have disproportionately longer than small males. It is generally assumed such scaling relationships ('static allometries') are insensitive short–term changes environment, and for this reason they regularly used as diagnostic attributes populations species. Here I report breeding experiments on horned...

Beetle horns are enlarged outgrowths of the head or thorax that used as weapons in contests over access to mates. Horn development is typically confined males (sexual dimorphism) and often only largest (male dimorphism). Both types dimorphism result from endocrine threshold mechanisms coordinate cell proliferation near end larval period. Here, we map presence/absence each type onto a recent phylogeny for genus Onthophagus (Coleoptera: Scarabaeidae) explore how horn has changed time. Our...

Sexual dimorphisms in trait expression are widespread among animals and especially pronounced ornaments weapons of sexual selection, which can attain exaggerated sizes. Expression traits is usually male-specific nutrition sensitive. Consequently, the developmental mechanisms generating sexually dimorphic growth nutrition-dependent phenotypic plasticity each likely to regulate extreme structures. Yet we know little about how either these work, much less they might interact with other. We...

1. The Whale and the Virus: How Scientists Study Evolution.- 2. From Natural Philosophy to Darwin: A Brief History of Evolutionary Ideas.- 3. What Rocks Say: Geology Paleontology Reveal Life.- 4. Tree Life: Biologists Use Phylogeny Reconstruct Deep Past.- 5. Raw Material: Heritable Variation among Individuals.- 6. Ways Change: Drift Selection.- 7. Beyond Alleles: Quantitative Genetics Evolution Phenotypes.- 8. Selection: Empirical Studies in Wild.- 9. Our Genes.- 10. Adaptation: Genes...

For almost a century, biologists have used trait scaling relationships (bi-variate scatter-plots of size versus body size) to characterize phenotypic variation within populations, and compare animal shape across populations or species. Scaling are popular metric because they long been thought reflect underlying patterns growth development. However, the physiological mechanisms generating not well understood, it is yet clear how evolve. Here we review recent advances in developmental biology,...

The morphological diversity of insects is one the most striking phenomena in biology. Evolutionary modifications to relative sizes body parts, including evolution traits with exaggerated proportions, are responsible for a vast range forms. Remarkable examples an insect trait proportions mandibular weapons stag beetles. Male beetles possess extremely enlarged mandibles which they use combat rival males over females. As other sexually selected traits, beetle vary widely size among males, and...