Summary: Hourigan & Reese (1987)

The Hawaiian archipelago is an extremely isolated island group. Hourigan & Reese (1987) noted that the Hawaiian fish fauna is derived from, and has close affinities with, the Indo-west Pacific fauna. However, while it has many endemic species (30% of inshore fishes), there is low species diversity (depauperate). There is local adaptation, but no species radiation. These trends may have been caused by: (1) geographic isolation and current patterns; (2) life history characteristics, particularly dispersal ability, of the fishes; and (3) the extent of adaptive differentiation. Hourigan & Reese (1987) suggested that the isolation of Hawaii is due to its location with respect to unfavourable pacific current patterns, which in turn, determines the marine faunal source.

Summary: Skelhorn (2011)

Noxious prey may use conspicuous colour patterns to advertise their defences (chemical or physical) to predators (aposematic colouring) and predators may show unlearned biases against these warning colours. Predators may use additional signals (.e.g sounds and odours) to determine attack rate and may decreases attack rates when the risk of ingestion toxic prey is perceived to be high. If a cue reliably signals prey defense, this should incite biases by predators against warningly coloured food. Skelhorn (2011) tested whether observation of a conspecific's distaste response to a bitter-tasting solution (e.g. beak wiping, head shaking) caused chicks (Gallus gallus) to bias their foraging decisions away from warningly colour prey. Chicks that observed a distaste reaction attacked fewer red and yellow crumbs, and more green crumbs. Observing a disgust response caused observers to bias their foraging preferences away from warningly coloured food. Skelhorn (2011) suggests that a predator's social system may be important in the evolution of prey defences.

Summary: Li & Zhang (2010)

In 1964, Hamilton suggested that kin recognition might be important for mediating the evolution of altruistic behaviour. Li & Zhang (2010) investigated amicable and agonistic social behaviours in Brandt's voles (Lasiopodomys brandti) to determine the mechanism of parent-offspring recognition (prior association / familiarity vs. phenotypic matching). Familiarity involves identification of kin by prior association with them, while phenotypic matching involves identification of kin based on shared family characteristics. Li & Zhang (2010) first examined whether parents could distinguish own from alien offspring, and found that both males and females showed more agonistic behaviour to alien young, indicating discrimination of young. They then used a cross fostering paradigm to investigate the underlying recognition mechanism. They found that parents are more amicable to familiar offspring and more agonistic to unfamiliar offspring (both accounts regardless of relation). Their results suggest that the most likely recognition mechanism in Brandt's voles is familiarity.

Summary: Edvardsson & Arnqvist (2000)

To stimulate females, males may engage in courtship behaviours during and after copulation. When females impose biases on postmating paternity success, thereby varying male reproductive success, these behaviours may evolve by cryptic female choice. Edvardsson & Arnqvist (2000) maniuplated female perception of male courtship behaviour in the red flour beetle Tribolium castaneum by male tarsal ablation (males could still perform courtship behaviour but could not stimulate females) and quantified male copulatory behaviour to determine whether females cause positive relationships between male copulatory courtship behaviour and relative fertilization success. They found that leg manipulation did not impair male vigour or number of sperm transferred. However, they did find a positive relationship between intensity of courtship and relative fertilization success: manipulated males had lower fertilization success. Female perception of male courtship behaviour, rather than actual male behaviour, governs sperm competition, showing that females impose biases on postmating paternity success and that copulatory courtship is under sexual selection (typically concerned with precopulatory processes and variance in male mating success) by cryptic female choice.

Summary: Bos et al. (2009)

Mate selection is important in many organisms and occurs through multiple trait assessment in a context or condition-dependent manner. Theoretically, mate choice may be based on an individual's genotype, but this requires organisms to self-reference their own genotype. MHC genes may be used in self-referencing as they can be assessed through ligand binding in the vomeronasal organ. Due to overdominance, major histocmpatibility complex (MHC) alleles are likely to be adaptive and there is likely to be negative assoratative mating between individuals. Bos et al. (2009) assessed MHC-based mating preferences in wild, outbred eastern tiger salamanders (Ambystoma tigrinum tigrinum) by genotyping adults and larvae at microsatellite and MHC loci. They aimed to address 4 questions about MHC-based mate choice: 1) Do morphological characteristics increase reproductive success? 2) Is reproductive success in males mediated by the MHC? 3) If yes, are the mating patterns context-dependent? 4) If yes (2 and 3), is variation in male reproductive success linked to MHC-based cues only when large differences are apparent? Bos et al. (2009) found that male reproductive success was positively correlated with increased tail length.They found that MHC-similar males (to females) sired more offspring, indicating that negative assortative mating is not occurring in the population and that MHC-diverent males may be at a reproductive disadvantage. Bos et al. (2009) suggest that MHC-based choice is likely to be influenced by many factors.

Summary: Honda-Sumi (2005)

Cricket songs are species-specific signals important for species recognition, mate choice and male advertisement. Honda-Sumi (2005) compared the calling songs of 3 Japanese crickets to validate the function of acoustic signals (i.e. calling song) as a premating isolation mechanism between sympatric species using playback experiments. Teleogryllus emma is widely distributed and is sympatric with both T. yezoemma (North) and T. taiwanemma (South), while T. yezoemma and T. taiwanemma are allopatric. Hondu-Sumi (2005) compared three temporal parameters, 1 frequency parameter and two structural parameters to test for species divergence in signals and also tested whether female T. taiwanemma distinguish conspecific males. Sympatric species had divergent songs, while allopatric species had similar songs. T. taiwanemma females could discriminate conspecifics (i.e. showed positive phonotaxis). This suggests that, where hybridization is costly, calling song is an important premating isolation barrier in sympatric Teleogryllus species.

Summary: Ahearn et al. 1974

Ahearn et al. (1974) identified two kinds of reproductive isolating mechanisms: 1) premating isolation barriers (in the form of behavioural/ethological isolation); and 2) postmating isolation barriers (male hybrid sterility). They suggest that reproductive isolation arises as a by-product of genetic divergence or is induced by natural selection as a gene exchange barrier. Thus, premating isolation should occur more often between sympatric species. Drosophila heteroneura and D. silvestris are sympatric fly species on the island of Hawaii, while D. planitibia is allopatric on nearby Maui. Ahearn et al. (1974) found pronounced behavioural isolation between the sympatric, but not the allopatric, species. They did note that D. planitibia females do discriminate against D. heteroneura males. Male bybrid sterility is seen in allopatric crosses and is not correlated with behavioural isolation. They suggest that this is expected if premating isolation between closely related species is an ad hoc production of natural selection, while postmating isolation is an incidental result of genetic divergence.