Biology subjects

Montgomery, S. H.

Publications and source records attributed to Montgomery, S. H..

40 records · Page 3Linked to original sources

bioRxiv2020

Heliconiini butterflies can learn time-dependent reward associations

For many pollinators, flowers provide predictable temporal schedules of resource availability, meaning an ability to learn time-dependent information could be widely beneficial. However, this ability has only been demonstrated in a handful of species. Observational studies of Heliconius butterflies suggest that they may have an ability to form time-dependent foraging preferences. Heliconius are unique among butterflies in actively collecting and digesting pollen, a dietary behaviour linked to spatiotemporally faithful ‘trap-line’ foraging. Time-dependency of foraging preferences is hypothesised to allow Heliconius to exploit temporal predictability in alternative pollen resources, as well as contributing to optimal use of learnt foraging routes. Here, we provide the first experimental evidence in support of this hypothesis, demonstrating that Heliconius hecale can learn opposing colour preferences in two time periods. This shift in preference is robust to the order of presentation, suggesting that preference is tied to the time of day and not due to ordinal learning. However, we also show that this ability is not limited to Heliconius, as previously hypothesised, but is also present in a related genus of non-pollen feeding butterflies. This demonstrates that time learning pre-dates the origin of pollen-feeding and may be prevalent across butterflies with less specialized foraging behaviours.Competing Interest StatementThe authors have declared no competing interest.View Full Text

animal behavior and cognition↗

bioRxiv2020

An agent-based model clarifies the importance of functional and developmental integration in shaping brain evolution

Comparisons of vertebrate brain structure suggest a conserved pattern of scaling between components, but also many examples of lineages diverging dramatically from these general trends. Two competing hypotheses of brain evolution seek to explain these patterns of variation by invoking either ‘external’ processes, such as selection driving phenotypic change, or ‘internal’ processes, like developmental coupling among brain regions. Efforts to reconcile these views remain deadlocked, in part due to empirical under-determination and the limitations of ‘relative significance’ debates. We introduce an agent-based model that allows us to simulate brain evolution in a ‘bare-bones’ system and examine the dependencies between variables that may shape brain evolution. Our simulations formalise verbal arguments and interpretations concerning the evolution of brain structure. We illustrate that ‘concerted’ patterns of brain evolution cannot alone be taken as evidence for developmental coupling, or constraint, despite these terms often being treated as synonymous in the literature. Both developmentally coupled and uncoupled brain architectures can represent adaptive mechanisms, depending on the distribution of selection across the brain, life history, and the relative costs of neural tissue. Our model also illustrates how the prevalence of mosaic and concerted patterns of evolution may fluctuate through time in a variable environment, which we argue implies that developmental coupling is unlikely to be a significant evolutionary constraint.Competing Interest StatementThe authors have declared no competing interest.View Full Text

evolutionary biology↗

bioRxiv2020

Neural processing genes are linked to divergence in visual mate preference in sympatric Heliconius butterflies

Many animal species remain separate not because they fail to produce viable hybrids, but because their individuals choose not to mate. However, we still know very little of the genetic mechanisms underlying changes in these mate preference behaviours. Heliconius butterflies display bright warning patterns, which they also use to recognize conspecifics. Here, we couple QTL for divergence in visual preference behaviours with population genomic and gene expression analyses of neural tissue (central brain, optic lobes and ommatidia) across development in two sympatric Heliconius species. Within a region containing 200 genes, we identify five genes that are strongly associated with divergent visual preferences. Three of these have previously been implicated in key components of neural signalling (specifically an ionotropic glutamate receptor and two regucalcins), and overall our candidates suggest shifts in behaviour involve changes in visual integration or processing. This would allow preference evolution without altering perception of the wider environment.

evolutionary biology↗

bioRxiv2017

Beyond Brain Size

Despite prolonged interest in comparing brain size and behavioral proxies of intelligence across taxa, the adaptive and cognitive significance of brain size variation remains elusive. Central to this problem is the continued focus on hominid cognition as a benchmark, and the assumption that behavioral complexity has a simple relationship with brain size. Although comparative studies of brain size have been criticized for not reflecting how evolution actually operates, and for producing spurious, inconsistent results, the causes of these limitations have received little discussion. We show how these issues arise from implicit assumptions about what brain size measures and how it correlates with behavioral and cognitive traits. We explore how inconsistencies can arise through heterogeneity in evolutionary trajectories and selection pressures on neuroanatomy or neurophysiology across taxa. We examine how interference from ecological and life history variables complicates interpretations of brain-behavior correlations, and point out how this problem is exacerbated by the limitations of brain and cognitive measures. These considerations, and the diversity of brain morphologies and behavioral capacities, suggest that comparative brain-behavior research can make greater progress by focusing on specific neuroanatomical and behavioral traits within relevant ecological and evolutionary contexts. We suggest that a synergistic combination of the bottom up approach of classical neuroethology and the top down approach of comparative biology/psychology within closely related but behaviorally diverse clades can limit the effects of heterogeneity, interference, and noise. We argue this shift away from broad-scale analyses of superficial phenotypes will provide deeper, more robust insights into brain evolution.

animal behavior and cognition↗