Variation In Ornamentation Research Articles

The immunocompetence handicap hypothesis: testing the genetic predictions

The immunocompetence handicap hypothesis suggests that the immune system competes for resources with sexually selected ornaments; variation in ornaments might reflect genetic variation for immunocompetence. We tested this genetic prediction by mating scorpionfly females to males differing in the expression of a condition-dependent ornament trait, saliva secretion, and then comparing offspring immunocompetence. We found several indications of an immunocompetence handicap in our study: females had superior immunocompetence compared with males, the different immune traits were positively correlated, and there were indications of genetic variation in immune traits. However, we found no significant difference in the immunocompetence of offspring derived from males differing in ornament expression, only a tendency for sons of ornamented males to possess slightly better immunocompetence. The estimated effect of fathers on offspring immunocompetence was rather small, but it might be a sufficient benefit of female choice, provided that the costs of choice are small. We conclude that the genetic benefit of female choice is small concerning offspring immunocompetence, but the immunocompetence handicap principle might nevertheless work in scorpionflies.

Intraspecific variation in the shell ornamentation of benthic Ostracoda (Crustacea) from Kiribati, Pacific Ocean

Twenty four species of ostracod have been found on Tarawa Atoll and fifteen on Kuria Island, Republic of Kiribati in the western Pacific Ocean. Thirteen species are common to both atolls. A consistent difference has been discovered in the ostracod faunas of Tarawa and Kuria, with those from Kuria showing coarser texture in the ornamentation than their counterparts from Tarawa. The variation of carapace ornamentation has led to multiple names for a species. A characteristic ornamentation at a particular locality may be a due to a small number of specimens colonising the new locality and having a limited gene pool. Alternatively, any variation in the ornamentation may be a clue to multiple phases of colonisation within a small area.

Possible latitudinal predation gradient in middle Paleozoic oceans

Research Article| January 01, 1999 Possible latitudinal predation gradient in middle Paleozoic oceans Lindsey R. Leighton Lindsey R. Leighton 1Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 48109, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Lindsey R. Leighton 1Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 48109, USA Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1999) 27 (1): 47–50. https://doi.org/10.1130/0091-7613(1999)027<0047:PLPGIM>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Lindsey R. Leighton; Possible latitudinal predation gradient in middle Paleozoic oceans. Geology 1999;; 27 (1): 47–50. doi: https://doi.org/10.1130/0091-7613(1999)027<0047:PLPGIM>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Molluscan ornament in modern oceans increases with decreasing latitude, in response to greater risk from tropical durophages (shell-crushing predators). The latitudinal gradient is presumed to be associated with the appearance of modern durophages during the Cretaceous, but this is untested. A radiation of durophages during the Devonian may have resulted in sufficient predation pressure to influence prey distribution similarly, although Devonian predators and prey are distantly related to their recent equivalents. This study examines latitudinal variation in ornament in Devonian strophomenide brachiopods to determine if a latitudinal gradient existed. A latitudinal gradient is documented for the Devonian; ornament decreases with increasing latitude. The correlation between proportion of spinose genera and region is −0.947 (p < 0.001). Similar to modern molluscs, spinose strophomenide genera constitute 26%–41% of tropical genera. The data corroborate the hypothesis that predation influenced the evolution and distribution of prey as early as the Devonian Period. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Le tégument des graines chez les Lupinus (Fabaceae) de Tunisie

Summary Study of integument, using light and scanning electron microscopy, in the seeds of five species of Lupines growing in Tunisia revealed anatomical structure similar to that of most Papilionaceae: a layer of Malphigian cells, a layer of hourglass—shaped cells and a parenchyma layer. Analysis of the surface of the integument revealed four types of ornamentation: 1) a crater shape in L. angustifolius L.; 2) foveolate in L. albus L. cv. Mekna; 3) protuberances not exceeding 10 μm in diameter in L. angustifolius L., L. luteus L. and L. micranthus Guss, and 4) protuberances 160|jm in diameter in L. cosentina Guss. It also revealed intraspecific variation in ornamentation in L. angustifolius L., intraspe- cific stability in L. luteus L. and L. cosentina Guss, and interspecific similarity for L cosentina Guss, and the Lupines belonging to the rough seed group.

Diversification of spore-pollen “character states” in the Indian Permian

The circumscription of palynomorphs depends on our understanding of “character states”. In time, a character appears, distinguishes itself and proliferates. This paper attempts to delineate certain important characters found in palynomorphs of the Permian sequence of India, which commenced with a glaciogenic event followed by warm humid climate and terminated in relatively cooler and dry condition. The intervening time of c. 40 Ma witnessed a gradual amelioration of the climate which resulted in the proliferation of the Glossopteris flora. An analysis of some important characters of palynomorphs revealed major trends of diversification. The simple girdling monosaccate organization, as in Plicatipollenites, Parasaccites, and Virkkipollenites, was prevalent in the Early Asselian Lower Talchir Formation. Subsequently, during the Upper Talchir and Lower Karharbari Formations, varied architectures evolved in the mode of saccus attachment and its symmetry (such as in Crucisaccites, Divarisaccus, and Stellapollenites), although the basic plan of morphology remained monosaccate. Bisaccate pollen with simple striations (e.g. Crescentipollenites) also appeared in the Lower Talchir Formation. Certain characteristic features, such as vertical partitions and reticuloid arrangements of striations, appeared subsequently in the forms with basic bisaccate organization and are recognised in Rhizomaspora, Lahirites, and Verticipollenites. Taeniate morphology (as in Lueckisporites) first appeared at the top of the Karharbari Formation, followed by Lunatisporites in the Raniganj Formation and proliferated in the Lower Triassic Panchet Formation. The upper part of the Talchir and Lower Karharbari Formations became distinct by the advent of several spore morphologies, such as zona (in Indotriradites), cingulum (in Dentatispora), and the trilete apparatus expension imitating the saccus (sub-infraturma Varitrileti). All these characters are considered as dispersal aiding morphologies. Other trends of diversification through time (such as increasing variation of ornamentation and their differential distribution) appeared in Microbaculispora, Brevitriletes, Microfoveolatispora, and Didecitriletes. The analysis of palyno-assemblages based on evolutionary character states holds a high potential for precise biostratigraphy.

Ornament and body size variation and their measurement in natural populations

Measurement of intrapopulation variation in secondary sexual traits is a priority in the testing of sexual selection models. However, it is important to take care in the choice of materials and delimitation of populations. The use of museum skins to study variation in male tail ornaments may substantially underrepresent the real degree of intrapopulation variation. Data from live animals in specific areas provide more realistic estimates, and should be used whenever possible. I use as an example field data on male ornament length and body size in Vidua macroura (Aves: Ploceidae), a promiscuous, parasitic African finch with elongated tail plumes. Individual males differ in the timing and rate of ornament growth, and females are therefore faced with a large degree of phenotypic variation in male ornament size, even though genetic variation may not be great. By correcting for seasonal variation in the ornament lengths of males caught at different times, I show that mid-season coefficients of variation in ornament length of breeding males in two populations are as high as 18% and 55%. By contrast, tarsus, wing and unornamented tail lengths of the same males vary from 2 to 4%.

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.