Our new paper on "Trilobite pelotons" published by the journal, Paleontology, is now out.
Although it remains a hypothesis, the findings of the paper support the "variation range hypothesis", the notion that there is a relationship between the energy saving quantity and the size range among a group of organisms where there is an energy saving mechanism. I first explored this (with Matjaz Perc) across a range of organisms in our paper "Energy saving mechanisms in biological systems".
The variation range hypothesis is simple and intuitive. Weaker individuals can sustain speeds set by stronger individuals by exploiting the available energy saving mechanism. So, these individuals can be weaker to a degree that is roughly proportionate to the energy saving quantity. In the paper, we summarize it this way:
"The variation range hypothesis posits that the size range among individuals in
groups corresponds proportionately to the energy saving quantity (as a per cent)
because weaker, smaller, individuals sustain speeds of stronger, larger, individuals by
exploiting the energy saving mechanism. We determine size range by
SR = [(BLmax – BLmin) / BLmax] * 100, (1)
where SR is size range, and BL is body-length. As discussed further, this allows
comparisons between size ranges and energy saving as a per cent, shown as equation
(8).
Individuals too small to fit within this range become isolated from the group and may
perish, or form sub-groups of narrower size ranges, as has been modelled by Trenchard
et al. (2015) in the context of bicycle pelotons.
In the wider context of migration as a
factor that drives speciation (Winker 2000), we consider the possibility that this form of
group-sorting may contribute to migratory divergence and to reproductive isolation, as
proposed by Delmore et al. (2012).
Speyer & Brett (1985) reported that individuals within trilobite groups generally fall within
a rather narrow size range, a finding which tends to support the variation range
hypothesis. Moreover, the presence of any similarly sized trilobites of other species
mixed with clusters of another species also tends to support the variation range
hypothesis, since such individuals would likely have possessed similar power and
speed capacities."
