Heritability of anti‐predatory traits: vigilance and locomotor performance in marmots

Animals must allocate some proportion of their time to detecting predators. In birds and mammals, such anti‐predator vigilance has been well studied, and we know that it may be influenced by a variety of intrinsic and extrinsic factors. Despite hundreds of studies focusing on vigilance and suggestions that there are individual differences in vigilance, there have been no prior studies examining its heritability in the field. Here, we present one of the first reports of (additive) genetic variation in vigilance. Using a restricted maximum likelihood procedure, we found that, in yellow‐bellied marmots (Marmota flaviventris), the heritability of locomotor ability (h² = 0.21), and especially vigilance (h² = 0.08), is low. These modest heritability estimates suggest great environmental variation or a history of directional selection eliminating genetic variation in these traits. We also found a significant phenotypic (r_P = ?0.09 ± 0.04, P = 0.024) and a substantial, but not significant, genetic correlation (r_A = ?0.57 ± 0.28, P = 0.082) between the two traits (slower animals are less vigilant while foraging). We found no evidence of differential survival or longevity associated with particular phenotypes of either trait. The genetic correlation may persist because of environmental heterogeneity and genotype‐by‐environment interactions maintaining the correlation, or because there are two ways to solve the problem of foraging in exposed areas: be very vigilant and rely on early detection coupled with speed to escape, or reduce vigilance to minimize time spent in an exposed location. Both strategies seem to be equally successful, and this ‘locomotor ability‐wariness’ syndrome may therefore allow slow animals to compensate behaviourally for their impaired locomotor ability.     

Visual fields,foraging and collision vulnerability in Gyps vultures

The visual fields of vultures contain a small binocular region and large blind areas above, below and behind the head. Head positions typically adopted by foraging vultures suggest that these visual fields provide comprehensive visual coverage of the ground below, prohibit the eyes from imaging the sun and provide extensive visual coverage laterally. However, vultures will often be blind in the direction of travel. We conclude that by erecting structures such as wind turbines, which extend into open airspace, humans have provided a perceptual challenge that the vision of foraging vultures cannot overcome.     

The relationship between introduced European Starlings and the reproductive activities of Mountain Bluebirds and Tree Swallows in British Columbia,Canada

The European Starling Sturnus vulgaris is an introduced species in North America and is an aggressive competitor for tree cavity nest‐sites. Starlings are commonly considered to influence nest‐site selection and reproductive success of native cavity‐nesting species negatively. We examined the relationship between Starling nest density and the fecundity of two native secondary cavity‐using passerines, Mountain Bluebird Sialia currucoides and Tree Swallow Tachycineta bicolor. We monitored a total of 622 nests (approximately equal numbers for each of the three species) in woodpecker‐excavated and naturally occurring cavities in 29 small forest groves in central British Columbia, Canada, between 2000 and 2009. The dimensions of cavities used and the timing of nest initiation overlapped for all species, although Starlings initiated clutches earliest. Mixed‐effects models were used to assess whether nest abundance, clutch size or nest success were affected directly by Starling nest abundance, or indirectly via a shift in cavity selection or timing of breeding. Starlings and Mountain Bluebirds showed inverse trends in nest abundance. Mountain Bluebird clutch sizes were smaller if they were initiated later in the breeding season. There was weak evidence that Tree Swallow clutch size decreased with cavity depth when Starling nests were abundant, and increased with cavity depth where there were few Starling nests. We conclude that despite the aggressive nature of this exotic cavity‐nester, the influence of Starlings on native secondary cavity‐nesting passerines is modest where cavities are abundant.     

Large‐scale evolutionary trends of Acrochordiceratidae Arthaber, 1911 (Ammonoidea,Middle Triassic) and Cope’s rule

Abstract: Directed evolution of life through millions of years, such as increasing adult body size, is one of the most intriguing patterns displayed by fossil lineages. Processes and causes of such evolutionary trends are still poorly understood. Ammonoids (externally shelled marine cephalopods) are well known to have experienced repetitive morphological evolutionary trends of their adult size, shell geometry and ornamentation. This study analyses the evolutionary trends of the family Acrochordiceratidae Arthaber, 1911 from the Early to Middle Triassic (251–228 Ma). Exceptionally large and bed‐rock‐controlled collections of this ammonoid family were obtained from strata of Anisian age (Middle Triassic) in north‐west Nevada and north‐east British Columbia. They enable quantitative and statistical analyses of its morphological evolutionary trends. This study demonstrates that the monophyletic clade Acrochordiceratidae underwent the classical evolute to involute evolutionary trend (i.e. increasing coiling of the shell), an increase in its shell adult size (conch diameter) and an increase in the indentation of its shell suture shape. These evolutionary trends are statistically robust and seem more or less gradual. Furthermore, they are nonrandom with the sustained shift in the mean, the minimum and the maximum of studied shell characters. These results can be classically interpreted as being constrained by the persistence and common selection pressure on this mostly anagenetic lineage characterized by relatively moderate evolutionary rates. Increasing involution of ammonites is traditionally interpreted by increasing adaptation mostly in terms of improved hydrodynamics. However, this trend in ammonoid geometry can also be explained as a case of Cope’s rule (increasing adult body size) instead of functional explanation of coiling, because both shell diameter and shell involution are two possible paths for ammonoids to accommodate size increase.     

Pollination efficiency and reproductive patterns in relation to local plant density,population size,and floral display in the rewarding Listera ovata (Orchidaceae)

Pollination efficiency and reproductive success vary strongly among populations of most animal‐pollinated plant species, depending on their size and local density, whereas individual plants within populations experience varying levels of reproductive output as a result of differences in floral display. Although most orchid species have been shown to be severely pollination limited, few studies have investigated the impact of the above‐mentioned factors on pollination success and reproduction, especially in rewarding species. In this study, the impact of population size, local density of flowering plants, and floral display on the rates of pollinia export and fruit production was investigated in 13 natural populations of the rewarding terrestrial orchid Listera ovata. In addition, an emasculation experiment was set up to examine how floral display and local density of flowering plants affected the relative importance of cross‐ vs. geitonogamous pollination in determining fruit set. In the studied populations, pollination efficiency, pollen removal, and fruit set increased with increasing population size until a threshold value of 30–40 flowering plants was reached, above which pollination efficiency and reproductive output decreased again. On average, plants with large floral displays showed higher proportional pollinia removal and fruit set compared with smaller plants. Fruit production was also significantly and positively related to local plant density, whereas emasculation did not affect the relationship between local plant density and fruit set, suggesting that geitonogamous pollination did not affect the outcome of female function. The results of this study are discussed in the light of the flowering mechanism of the species and its generalized pollination system. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 713–721.