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Renee M Borges

Publications and source records attributed to Renee M Borges.

5 recordsLinked to original sources
PubMed2005

Searching on patch networks using correlated random walks: space usage and optimal foraging predictions using Markov chain models.

We describe a novel representation of a discrete correlated random walk as the transition matrix of a Markov chain with the displacements as the states. Such a representation makes it possible to utilize results from the theory of absorbing Markov chains, to make biologically interesting predictions without having to resort to Monte Carlo simulations. Our motivation for constructing such a representation is to explore the relationship between the movement strategy of an animal searching for resources upon a network of patches, and its consequent utilization of space and foraging success. As an illustrative case study, we have determined the optimal movement strategy and the consequent usage of space for a central place forager utilizing a continuous movement space which is discretized as a hexagonal lattice. The optimal movement strategy determines the size of the optimal home range. In this example, the animal uses mnemokinesis, which is a sinuosity regulating mechanism, to return it to the central place. The movement strategy thus refers to the choice of the intrinsic path sinuosity and the strength of the mnemokinetic mechanism. Although the movement space has been discretized as a regular lattice in this example, the method can be readily applied to naturally compartmentalized movement spaces, such as forest canopy networks. This paper is thus an attempt at incorporating results from the theory of random walk-based animal movements into Foraging Theory.

Animals↗
PubMed2005

The fitness consequences of bearing domatia and having the right ant partner: experiments with protective and non-protective ants in a semi-myrmecophyte.

The fitness advantage provided by caulinary domatia to myrmecophytes has never been directly demonstrated because most myrmecophytic species do not present any individual variation in the presence of domatia and the removal of domatia from entire plants is a destructive process. The semi-myrmecophytic tree, Humboldtia brunonis (Fabaceae: Caesalpinioideae), is an ideal species to investigate the selective advantage conferred by domatia because within the same population, some plants are devoid of domatia while others bear them. Several ant species patrol the plant for extra-floral nectar. Fruit production was found to be enhanced in domatia-bearing trees compared to trees devoid of domatia independent of the ant associate. However, this domatium effect was most conspicuous for trees associated with the populous and nomadic ant, Technomyrmex albipes. This species is a frequent associate of H. brunonis, inhabiting its domatia or building carton nests on it. Ant exclusion experiments revealed that T. albipes was the only ant to provide efficient anti-herbivore protection to the leaves of its host tree. Measures of ant activity as well as experiments using caterpillars revealed that the higher efficiency of T. albipes was due to its greater patrolling density and consequent shorter lag time in attacking the larvae. T. albipes also provided efficient anti-herbivore protection to flowers since fruit initiation was greater on ant-patrolled inflorescences than on those from which ants were excluded. We therefore demonstrated that caulinary domatia provide a selective advantage to their host-plant and that biotic defence is potentially the main fitness benefit mediated by domatia. However, it is not the sole advantage. The general positive effect of domatia on fruit set in this ant-plant could reflect other benefits conferred by domatia-inhabitants, which are not restricted to ants in this myrmecophyte, but comprise a large diversity of other invertebrates. Our results indicate that mutualisms enhance the evolution of myrmecophytism.

Animals↗
PubMed2005

Do plants and animals differ in phenotypic plasticity?

This paper compares the flexibility in the nexus between phenotype and genotype in plants and animals. These taxa although considered to be fundamentally different are found to be surprisingly similar in the mechanisms used to achieve plasticity. Although non-cognitive behaviour occurs in plants, its range is limited, while morphological and developmental plasticity also occur to a considerable extent in animals. Yet both plants and animals are subject to unique constraints and thus need to find unique solutions to functional problems. A true comparison between the plant and animal phenotype would be a comparison between plants and sessile photosynthesizing colonial invertebrates. Such comparisons are lacking. However, they would provide important insights into the adaptive significance of plasticity in these groups. It is also suggested that a comparison of inflexible traits in these groups would provide an understanding of the constraints, as well as the costs and benefits,of a plastic versus non-plastic phenotype in plants and animals.

Adaptation, Physiological↗
PubMed2003

Butterfly pollination and high-contrast visual signals in a low-density distylous plant.

In low-density butterfly-pollinated Mussaenda frondosa (Rubiaceae), flowers attract pollinators at short distances while conspicuous, non-rewarding accessory bracts are detectable at long distances by long-ranging pollinators such as the birdwing butterfly Troides minos that did not detect flower-bearing plants in the absence of these bracts. However, even in the absence of flowers, the white, ultraviolet-absorbing bracts attracted butterflies that visited flowerless plants. Although flower visits by short-ranging territorial butterflies declined significantly on removal of bracts, they did not cease completely. Nectar-robbing carpenter bees and birds did not change their behaviour following bract removal. Bract removal caused a significant decline in fruit set, indicating their importance as visual signals to pollinators.

Animals↗