Simone here.
Before I start, I want to provide some links to my website and my supervisors' websites.
Today I'm going to write about Ecological Opportunity and how this concept relates to the three lizard colonists of White Sands. This topic has been the focus of my first field season so forgive me if I go on too long!
Let's start with a definition. I'm going to pull my definition from all over the place... and primarily from my head.
An ecological opportunity is basically anything that leads to the increased niche breadth of a species. For example, the evolution of a key innovation (that allows access to a new adaptive zone), the colonization of a novel environment, the extinction of antagonists (competitors, predators)... or some combination of the above. I should note that originally ecological opportunity was defined mostly in the context of release from competition pressures. And really, we can think of all of the above as relating to this in some context. A population might colonize a new environment without competitors, in the case of White Sands, for example.
I think this is a good opportunity (ha) to talk about my own research a bit. I am looking at White Sands as a potential setting for ecological release for the three species of lizard colonists. During my last field season I surveyed inside and outside White Sands to see if there was a significant reduction in the number of potential predators and competitors in the latter. Furthermore, I began to look for evidence of ecological release in one of the three colonist species: Sceloporus undulatus (see picture of male from White Sands above). I looked at whether sceloporus use of their microhabitat (perches) was more variable in White Sands compared to their use in ancestral dark populations.
My results have so far indicated that
1. the abundance of the total lizard population in White Sands is comparable to that in ancestral dark soils. This is cool because the former only has three species, whereas the latter has several- up to 10 or more. We use the term 'density compensation' to describe this increase in population size.
2. bird abundance also was higher outside White Sands- although I haven't yet classified this birds as potential competitors or predators (or neither)... and it will be interesting to see how this influences my results.
3. my results from quantifying sceloporus perches were provocative. Both sceloporus in dark soils and White Sands use their perches selectively... that is, not proportional to their availabilities in the habitats. However, White Sands lizards used a greater variety of their available* perches than did dark soils lizards. In other words, the DIVERSITY of perch use by White Sands sceloporus was higher than that of dark soils sceloporus.... cool!
This could suggest that there is some sort of alleviation from selective pressures in White Sands sceloporus. Perhaps the absence of interspecific competitors in White Sands allows the sceloporus there to expand their perch use. Perhaps research into diet and food resource use will demonstrate a similar trend... but that is for another field season.
*I say and mean available. This is an important point because, as Schluter says, resource heterogeneity may exist; that is, the 'depauperate communities' that are colonized not only have fewer competitors, but also may contain fewer available resources. This is likely the case in White Sands, where perches are far scarcer than in surrounding dark soils.
