Patterns of variation in tail ornament size in birds

In recent years several different kinds of sexual selection models have been developed, and tail ornaments in birds have frequently been used as an example of a sexually selected character where the models might apply. However, very little is known about intra- and interpopulation variation in ornament size. We have studied the elongated tail ornaments in four species of whydahs Vidua , the forktailed flycatcher Tyrannus savana and the Asian paradise flycatcher Terpsiphone paradisi. Ornaments were relatively longer in males with the longest tarsi ('heterogony' with positive allometry). Also, tail lengths were remarkably variable within each geographical area, the coefficient of variation (average = 11%) being three times as high as for body size characters. Models, with female preference of ornaments bearing no relation to male viability, usually generate lines of neutral equilibria. Thus, they predict extraordinary variation in ornaments between populations. However, elongated tail ornaments did not show higher geographical variation than the body size characters, suggesting that there is no line of equilibria for these ornaments.     

Convergence, recurrence and diversification of complex sperm traits in diving beetles (Dytiscidae)

Sperm display remarkable morphological diversity among even closely related species, a pattern that is widely attributed to postcopulatory sexual selection. Surprisingly few studies have used phylogenetic analyses to discern the details of evolutionary diversification in ornaments and armaments subject to sexual selection, and the origins of novel sperm traits and their subsequent modification are particularly poorly understood. Here we investigate sperm evolution in diving beetles (Dytiscidae), revealing dramatic diversification in flagellum length, head shape, presence of sperm heteromorphism, and the presence/type of sperm conjugation, an unusual trait where two or more sperm unite for motility or transport. Sperm conjugation was found to be the ancestral condition in diving beetles, with subsequent diversification into three forms, each exhibiting varying degrees of evolutionary loss, convergence, and recurrence. Sperm head shape, but not length or heteromorphism, was found to evolve in a significantly correlated manner with conjugation, consistent with the different mechanisms of head alignment and binding required for the different forms of conjugation. Our study reveals that sperm morphological evolution is channeled along particular evolutionary pathways (i.e., conjugate form), yet subject to considerable diversification within those pathways through modification in sperm length, head shape, and heteromorphism.     

Size of ornament is negatively correlated with baseline corticosterone in males of a socially monogamous colonial seabird

The Goymann–Wingfield model predicts that glucocorticoid levels in social animals reflect the costs of acquiring and maintaining social status. The crested auklet is one of the few avian colonial species where a mutual ornament in males and females is used in both sexual and aggressive displays. Previous studies of the crested auklet support the notion that the crest ornament is a badge of status in this species. Here, we examined the relationship between the crest ornament size and the adrenocortical function in breeding crested auklets. Crest length was negatively correlated with corticosterone at baseline in males, but not in females. Baseline corticosterone in females (but not in males) was negatively correlated with body condition index. Although male and female crested auklets are monomorphic in their ornamental traits, our results suggest that the socially mediated physiological costs associated with status signaling may differ between the sexes.     

Female mate choice and the potential for ornament evolution in túngara frogs Physalaemus pustulosus

The potential for ornament evolution in response to sexual selection rests on the interaction between the permissive-ness or selectivity of female preferences and the constraints on male development of signaling related traits. We investigate the former by determining how latent female preferences either exaggerate the magnitude of current traits (I.e. Elaborations) or favor novel traits (I.e. Innovations). In tungara frogs, females prefer complex mating calls (whine-chucks) to simple calls (whine only). The whine is critical for mate recognition while the chuck further enhances the attractiveness of the call. Here we use a combina-tion of synthetic and natural stimuli to examine latent female preferences. Our results show that a diversity of stimuli, including conspecific and heterospecific calls as well as predator-produced and human-made sounds, increase the attractiveness of a call when added to a whine. These stimuli do not make simple calls more attractive than a whine-chuck, however. In rare cases we found stimuli that added to the whine decrease the attractiveness of the call. Overall, females show strong preferences for both elaborations and innovations of the chuck. We argue that the emancipation of these acoustic adornments from mate recognition allows such female permissiveness, and that male constraints on signal evolution are probably more important in explaining why males evolved their specific adornment. Experimentally probing latent female preferences for stimuli out of the species' range is a useful means to gain insights about the potential of female choice to influence signal evolution and thus the astounding diversity in male sexually-selected traits.     

On the function of female ornaments: male bluethroats prefer colourful females

Female ornaments in animals with conventional sex roles have traditionally been considered non-functional, being merely a genetically correlated response to selection for male ornamentation. Alternatively, female ornaments may be influenced by selection acting directly on the females, either through female–female competition or male choice. We tested the latter hypothesis in mate choice experiments with bluethroats (Luscinia s. svecica), a passerine bird in which females vary considerably in coloration of an ornamental throat patch. In outdoor aviaries placed in prime breeding habitat, males were allowed to choose between a colourful and a drab female. We found that males associated more with, and performed more sexual behaviours towards, colourful females. Female coloration was not age-related, but correlated significantly with body mass and tarsus length. Thus, we have demonstrated both a male preference for female ornamentation, and a relationship between ornament expression and female body size, which may be indicative of quality. Our results refute the correlated response hypothesis and support the hypothesis that female ornamentation is sexually selected.     

On ornamental maturation of two Philippine hornbill species with a note on physiological colour change

Two Philippine hornbill species, the Visayan writhed-billed hornbill (Aceros waldeni) and the Visayan tarictic hornbill (Penelopides panini panini), display on their heads multiple sexual ornaments in both sexes. An account is given of the maturation of these ornaments, except for the hood on the hind neck, from the nestling stage through age 5 years in the writhed-bill, and from fledgling stage through age 3+ years in the tarictic. Development proceeds in a staggered fashion, in that component traits of the compound ornament are added sequentially to a baseline already present in the nestling (bare facial skin) up until maturity. In same-aged pair mates of the writhed-bill, elements (dark grooves and wreaths in the red bill) were continually added until the reproductive age of 5 years, when observations ceased. Contrary to published accounts, only the writhed-bill passes through a male-like plumage in the nestling/fledgling stage, whilst the tarictic juveniles attain their sexually dimorphic appearance right away. Writhed-bill chicks exhibit a colour dimorphism of eye (= iris) colour irrespective of sex, in which the two phases pass through two stages, but in reverse order. At least part of the ornaments can be interpreted as honest indicators of condition. Based on the concept of honest signalling, the multiple nature of the ornamentation is functionally explained by the multiple message hypothesis. A physiological colour change between white and blue within seconds/minutes occurs in the bare facial skin patches of the tarictic and thus adds to the arsenal of hornbill multiple ornaments. This constitutes the first evidence for this type of colour change in a bird.Communicated by F. BairleinThis paper is publication No. 54 of the Philippine Endemic Species Conservation Project of the Frankfurt Zoological Society. A word of thanks to Ernst Mayr: It is both a pleasure and an honour for me to be invited to humbly present to him a little piece of research. This appears truly fitting since Ernst has always taken an active interest in my research. This started when I was introduced to him in my early student days in Berlin in 1951 by our joint mentor, Erwin Stresemann. In his ornithological career Ernst had, in his awe-inspiring breadth of research, shown an active interest in the avifauna of the Philippines, of that world record treasure of biodiversity, when writing a book, together with Jean Delacour, on the Birds of the Philippines. In his usual generous manner, Ernst donated his last copy to me when I embarked on research and conservation in the Philippines 11 years ago. Though Ernst had followed my doings in science with benevolence from early on, his generous material support of our Philippines project became unrivalled among private donors, and it spurred our motivation immensely to carry on in what first appeared to be an almost hopeless situation, in a sea of a burgeoning population. I thank Ernst wholeheartedly for all his inspiration and farsighted support and wish him still many years to come.     

Timing of ornament growth, phenotypic variation, and size dimorphism in two promiscuous African whydahs (Ploceidae: Vidua)

Variation within populations is a prerequisite for the action of selection on morphological traits. Darwin assumed that there was much greater variation in sexual ornament size than in body size, but this may not be generally true of natural populations. I analyse field data on variation in body size and the length, area and mass of tail ornaments in paradise (Vidua paradisaea) and shaft-tailed whydahs (V. regia). Whydahs are promiscuous, brood parasitic African finches with elaborate tail ornaments in breeding males. The short, unadorned tails of male shaft-tailed whydahs, which carry a wire-like tail ornament, are non-significantly (1%) longer than female tails, but male paradise whydahs, which carry a large, broad ornament, have unadorned tails 10% longer than those of conspecific females. Fully grown ornament length, mass and area vary little more (CVs = 1.8-6.4%) than male or female body size traits (CVs = 1.7-6.1%). Instead, there is high variation in the timing of ornament development during prenuptial moult (CVs = 30.8–39.5% for paradise whydahs and 12.6–23.8% for shaft-tailed whydahs when corrected to a standard date). This temporal variation in development probably has greater significance for sexual selection in whydahs than maximum ornament size.     

Mechanics of sculpture formation in Magadiceramus? rangatira rangatira (Inoceramidae,Bivalvia) from the Upper Cretaceous of New Zealand

The surface sculpture of the inoceramid bivalve Magadiceramus? rangatira rangatira consists of commarginal ribs and curious, transverse wrinkles. The wrinkles typically are at a high angle or orthogonal to the shell margin (‘antimarginal’) and thus differ from purely radial structures. They show features of distribution and morphology that reveal them to be products of margin‐parallel compression of the shell‐secreting mantle and its adjacent, flexible, uncalcified periostracum. The interaction of wrinkles with commarginal ribs indicates that the ribs also formed as folds of the mantle margin. During growth, commarginal folding caused withdrawal of the entire mantle margin towards the umbo, with a consequent reduction in perimeter length. Measurement of specimens indicates that fabrication of the commarginal ribs resulted in the magnitude of commarginal shortening that is required for the formation of transverse wrinkles. We infer that early in ontogeny, at the first development of these sculptures, the wrinkles resulted entirely from mantle contraction and resultant commarginal shortening. With subsequent growth, total wrinkling included a component of ‘pre‐wrinkling’ inherited from the preceding growth stage; the contribution of pre‐wrinkling to total wrinkling increased with shell size. The proposed mechanical model is two‐phase. First, the transversely corrugated (pre‐wrinkled) mantle and periostracum advanced and secreted a slightly concave growth increment. Secondly, the mantle subsequently contracted to create a commarginal rib and increase the number and amplitude of transverse wrinkles. This model is consistent with a homogeneous mantle lacking any differentiated and specialized rib‐constructing segments.     

海城仙人洞遗址装饰品的穿孔技术及有关问题

本文在模拟制作穿孔装饰品的基础上，记述了不同方法穿孔在显微镜下观察到的特点，据此重新研究了海城仙人洞遗址出土装饰品的穿孔技术，修正了原研究者的一些看法。同时对装饰品穿孔方法的鉴定标准、穿孔效率、打磨齿根的目的等相关问题也作了讨论。