Abstract
<p>Flight is the primary form of locomotion for many avian species and is enabled by allometric scaling of morphological features such as wingspan, flight muscle size, and bone tensile strength. Contrary to this, the evolution of flightlessness in birds displays a selection towards an increase in body size with a reduction in flight associated features. The aim of this chapter is to explore the Loss of Dispersibility hypothesis as a cause for flightlessness in island birds, with consideration of the Island Rule and the Size-Constraint hypothesis. With island species paired with closest mainland relatives, comparative analyses were conducted comparing the change in wing loading ratios, wing lengths, and mass. With paired t-tests and Major Axis linear regression modelling, the hypotheses of isometric or allometric scaling in each of the features were tested. An increase in wing-loading ratio was apparent for many island species, as well as an increase in both mass and wing length. However, the rate of increase between mass and wing length is disproportionate, with mass increasing at a greater rate than wing length. These trends reject the Loss of Dispersibility hypothesis in support of the Size-Constraint hypothesis while providing little evidence for the Island Rule.</p>
Highlights
Galileo Galilei first characterised what is known to be allometry in his 1638 publication titled Dialogues Concerning Two New Sciences, where it was described that larger animals have thicker weight-bearing bones than smaller animals, such as those of elephants with their thick legs that are in stark contrast to mice with legs much smaller (Crew & de Salvio, 1991; Galilei, 1914)
The aim of this study is to examine three potentially influencing factors on the morphology of plants within the Coprosma genus: the triangular relationship of allometric scaling in leaf, petiole, and seed size, scaling relationships between reproductive structures of male and female flowers in diecious plants, as well as the effect of elevation on the applicability of Corner’s Rule on high altitude species
The results show that Coprosma species abide Corner’s Rule of allometric scaling, no relationships were found between floral features of males and females, as well as no evidence for a significant impact of elevation on the applicability of Corner’s Rule on high altitude plants
Summary
Galileo Galilei first characterised what is known to be allometry in his 1638 publication titled Dialogues Concerning Two New Sciences, where it was described that larger animals have thicker weight-bearing bones than smaller animals, such as those of elephants with their thick legs that are in stark contrast to mice with legs much smaller (Crew & de Salvio, 1991; Galilei, 1914). The second rule refers to a decrease in branch size and thickness with an increase in ramification (Corner, 1949) These complementary principles later became known as Corner’s Rules (Lauri, 2019). Results indicate strong allometric scaling relationships between stem thickness and leaf area, as well as a relatedness between a large seed producing a larger seedling that during maturation produces larger leaves. These three morphological features show evidence for allometric scaling across many woody species
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