Testing the influence of crushing-surface variation on seed cracking performance between beak morphs of the African seedcracker Pyrenestes ostrinus

Extreme phenotypic polymorphism is an oft-cited example of evolutionary theory in practise. Although these morphological variations are assumed to be adaptive, few studies have biomechanically tested such hypotheses. Pyrenestes ostrinus (the African seedcracker finch) shows an intraspecific polymorphism in beak size and shape that is entirely diet driven and allelically determined. Three distinct morphs feed upon soft sedge seeds during times of abundance, but switch to specializing on three different species of sedge seeds that differ significantly in hardness during lean times. Here we test the hypothesis that beak morphology is directly related to consuming seeds of different hardness. We used a novel experimental analysis to test how beak morphology affects the efficiency of cracking sedge seeds of variable hardness. We found that neither mandibular ramus width nor crushing surface morphology had significant effects on the ability to crack different seed types. It is likely that feeding performance is correlated with other aspects of beak size and shape such as beak depth and strength, muscle force, or gape. Our results highlight how even seemingly straightforward examples of adaptive selection in nature can be complex in practice.

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Genes controlling beak size and shape in Darwin's finches

AccessScience ◽

10.1036/1097-8542.yb170504 ◽

2017 ◽

Keyword(s):

Darwin's Finches ◽

Size And Shape ◽

Darwin’S Finches ◽

Beak Size

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Further Observations on the Morphology of Heterodera schachtii, with Remarks on the Bionomics of a strain attacking Mangolds in Britain

Journal of Helminthology ◽

10.1017/s0022149x00018733 ◽

1929 ◽

Vol 7 (3) ◽

pp. 119-140 ◽

Cited By ~ 14

Author(s):

Marjorie J. Triffitt

Keyword(s):

Sugar Beet ◽

Developmental Stages ◽

Morphological Characters ◽

Heterodera Schachtii ◽

Adult Males ◽

Morphological Variations ◽

Size And Shape ◽

Morphological Studies ◽

Comparative Survey

In a previous publication the morphological characters of a strain of H. schachtii specialised on the potato in Lincolnshire were discussed. The size and shape of the brown cysts, size of the eggs and first stage larvæ and the general characters of the adult males of this strain were compared with those of a strain attacking potatoes in Rostock, Mecklenburg, for which the specific name H. rostochiensis was suggested by Wollenweber 1923.Considerable dimensional variations were found to exist in the Lincolnshire strain, and a study of the literature on the morphological characters of H. schachtii specialised on sugar-beet and oats, showed equally wide divergencies between the findings of different workers. A certain amount of preserved material of infected roots of beet and oats being available to the writer, as many developmental stages as possible were extracted from these, on which similar morphological studies were carried out. Thus a fairly complete comparative survey of H. schachtii specialised on beet, oats and potatoes was completed, and the morphological variations between the strains were found to be insufficient to justify the separation of the strain specialised on potato from those on beet and oats. The name H. rostochicnsis was, therefore, deemed a synonym for H. schachtii.

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Evolution of European Cockchafers (Melolonthinae: Scarabaeidae: Coleoptera): a morphological, molecular and chromosomal study of intra- and inter-specific variations

Bulletin of Entomological Research ◽

10.1017/s0007485310000568 ◽

2011 ◽

Vol 101 (3) ◽

pp. 345-352 ◽

Cited By ~ 5

Author(s):

T. Giannoulis ◽

A.-M. Dutrillaux ◽

Z. Mamuris ◽

O. Montreuil ◽

C. Stamatis ◽

...

Keyword(s):

Gene Sequence ◽

Chromosomal Polymorphism ◽

Morphological Characters ◽

The Other ◽

Ancestral Karyotype ◽

Intraspecific Polymorphism ◽

Morphological Variations ◽

Chromosomal Study ◽

Sequence Study

AbstractIn cockchafers of the genus Melolontha, there is a marked intraspecific polymorphism for morphological characters, making some specimens of one species resemble another. A cytogenetic and molecular (mitochondrial COI gene sequence) study of typical and atypical forms of M. melolontha and M. hippocastani, captured at the same period and area, was performed. Karyotypes and haplotypes clearly characterize each taxon, placing atypical specimens in one or the other species unambiguously. This formally discards the role of hybridization in phenotypic resemblance, as usually proposed. Karyotypes and haplotypes were compared to those of M. pectoralis and Phyllophaga pleei, a more distantly related Melolonthinae, and some Dynastinae species, to reconstruct their ancestral karyotype. The karyotype of M. melolontha is the most derivative and that of P. pleei the most conserved among the Melolonthinae studied, which fits with the phylogeny established by COI gene analysis. Both karyotypes and COI haplotypes demonstrate the proximity of M. pectoralis and M. melolontha. The karyotype of M. melolontha is polymorphic, without relationship with morphological variations. Finally, the existence of similar morphological variations in different Melolontha species and chromosomal polymorphism in M. melolontha is discussed in relation with a network (reticulated) mode of speciation.

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Morphological variations of the shell of the bivalve Lucina pectinata (Gmelin, 1791)

JOURNAL OF ADVANCES IN BIOLOGY ◽

10.24297/jab.v10i2.6355 ◽

2017 ◽

Vol 10 (2) ◽

pp. 2092-2107 ◽

Cited By ~ 1

Author(s):

Emma MODESTIN

Keyword(s):

Morphometric Study ◽

Muddy Sediment ◽

Intraspecific Polymorphism ◽

Morphological Variations ◽

Lucina Pectinata ◽

Different Populations ◽

Muddy Sediments

In Martinique, the species Lucina pectinata (Gmelin, 1791) is called "mud clam, white clam or mangrove clam" by bivalve fishermen depending on the harvesting environment. Indeed, the individuals collected have differences as regards the shape and colour of the shell. The hypothesis is that the shape of the shell of L. pectinata (P. pectinatus) shows significant variations from one population to another. This paper intends to verify this hypothesis by means of a simple morphometric study. The comparison of the shape of the shell of individuals from different populations was done based on samples taken at four different sites. The standard measurements (length (L), width or thickness (E - Ã©paisseur) and height (H)) were taken and the morphometric indices (L/H; L/E; E/H) were established. These indices of shape differ significantly among the various populations. This intraspecific polymorphism of the shape of the shell of P. pectinatus could be related to the nature of the sediment (granulometry, density, hardness) and/or the predation. The shells are significantly more elongated in a loose muddy sediment than in a hard muddy sediment or one rich in clay. They are significantly more convex in brackish environments and this is probably due to the presence of more specialised predators or of more muddy sediments.

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Unbiased estimation of particle number and sizes using the new stereological tools: the disector, the fractionator, the selector, and the nucleator — or just point-sampled intercepts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104200 ◽

1988 ◽

Vol 46 ◽

pp. 428-429

Author(s):

H.J.G. Gundersen

Keyword(s):

Particle Number ◽

Small Distance ◽

Parallel Plane ◽

Unbiased Estimation ◽

Severe Problem ◽

New Era ◽

Size And Shape ◽

Distinct Property ◽

Sectioned Tissue

Previously, all stereological estimation of particle number and sizes were based on models and notoriously gave biased results, were very inefficient to use and difficult to justify. For all references to old methods and a direct comparison with unbiased methods see recent reviews.The publication in 1984 of the DISECTOR, the first unbiased stereological probe for sampling and counting 3—D objects irrespective of their size and shape, signalled the new era in stereology — and give rise to a number of remarkably simple and efficient techniques based on its distinct property: It is the only known way to obtain an unbiased sample of 3-D objects (cells, organelles, etc). The principle is simple: within a 2-D unbiased frame count or sample only cells which are not hit by a parallel plane at a known, small distance h.The area of the frame and h must be known, which might sometimes in itself be a problem, albeit usually a small one. A more severe problem may arise because these constants are known at the scale of the fixed, embedded and sectioned tissue which is often shrunken considerably.

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The influence of confocal microscope design on imaging performance

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146564 ◽

1993 ◽

Vol 51 ◽

pp. 144-145

Author(s):

C J R Sheppard

Keyword(s):

Image Quality ◽

Fluorescence Imaging ◽

Confocal Microscope ◽

Industrial Applications ◽

Three Dimensions ◽

Design Parameters ◽

Weak Signals ◽

Size And Shape ◽

Imaging Performance ◽

Fundamental Limitation

The confocal microscope is now widely used in both biomedical and industrial applications for imaging, in three dimensions, objects with appreciable depth. There are now a range of different microscopes on the market, which have adopted a variety of different designs. The aim of this paper is to explore the effects on imaging performance of design parameters including the method of scanning, the type of detector, and the size and shape of the confocal aperture.It is becoming apparent that there is no such thing as an ideal confocal microscope: all systems have limitations and the best compromise depends on what the microscope is used for and how it is used. The most important compromise at present is between image quality and speed of scanning, which is particularly apparent when imaging with very weak signals. If great speed is not of importance, then the fundamental limitation for fluorescence imaging is the detection of sufficient numbers of photons before the fluorochrome bleaches.

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