The final opportunity to gathering data for my MSc came to a quiet close on the 13th March 2013 after another week of wandering about the thorny shrublands of Rooipoort Nature Reserve, Near Kimberley. Although not successful in even the vaguest of definitions (well at least not for my work), my field assistant, Paula, and I did make some interesting observations and collected some DNA samples.
My study species, the Spotted sand lacertid (Pedioplanis lineoocellata), was incredibly scarce and we only sighted one definite individual- and a tiny one at that, possibly less than 4cm long.
This was in contrast to the previous two field excursions in which we found Pedioplanis in abundance. In April 2012, a trip lasting 3 weeks, we captured, marked and collected DNA from over 50 unique individual lizards, most of which were apparently juveniles. The previous 3 week excursion in October 2012, saw us capture over 60 unique individuals, all of which were adults. It appears- although without any hypothesis testing to support this- that an early March field trip was positioned awkwardly between the time the adults disappear and the juveniles begin hatching. Although I haven't found any mention of an annual life cycle in my study species (and I have seen at least two adult, gravid females active during April), there has been suggestions that the sympatric Ichnotropis squamulosa is an annual of sorts and does not live long after reproduction.
Interestingly, we caught six adult I. squamulosa in March 2013, only two during the April trip but none during the October-November 2012 trip. This could be an interesting case of temporal niche partitioning, the likes of which are often demonstrated among plant species forced to share limited pollinators (eg. Stone, Willmer, & Rowe, 1998), animals which would otherwise compete (Adams & Thibault, 2006) or sympatric lizards competing for the same food (Goldberg, 2008). Once again, these are just some 'itchy' ideas and by no means were these observations enough to make such conclusions. This would make an interesting study for an MSc student.
None of the above observations have anything to do with my project.
My project was intended to examine the relationship between real-time, actual movement of individuals within the reserve to the gene flow inferred from genetic differentiation in microsatellite loci. Researchers often use molecular markers to estimate gene flow and in some cases dispersal because such markers are easy and straight forward to collect, analyse and interpret whilst more direct measures of gene flow and movement are laborious, expensive and often impractical or impossible to perform. Although in common use, a simple inference of genetic distances to estimate gene flow/dispersal has its pitfalls including some unrealistic assumptions.
This project would aim to have a more direct comparison of the relationship between genetic differentiation as an estimate of gene flow (and indirectly, movement) to that measured from actual movement.
The microsatellite analysis for my species was fairly standard and included analysis like Least-Cost-Path analyses and Isolation-By-Distance. The Capture-Mark-Recapture work, however, was less standard. When first caught, lizards were marked with little number tags and a GPS co-ordinate was recorded and a photograph of the lizard taken. A GPS co-ordinate and a photograph was then taken every time the lizard was re-sighted.
The lizards were uniquely identified using the number tags and the photographs through spot-identification software . These unique individuals will be included in an analysis of movement based on the GPS co-ordinates for each sighting. When including a survey of local vegetation we can compare movement and gene flow estimates across the reserve using estimates of 'resistance' that each vegetation type may present.
Data collection in April was promising- both from a genetics and CMR point of view but two days before my October trip, we received news from reserve management that the site (and much of the rest of the reserve) had burnt. As a result of this we had to move sites, and such are the woes of a field biologist. Genetic sampling from the second site was decent but the CMR data collected was a bit fishy. My suspicions were more because it didn't seem to have the same pattern as that of the April dataset, that being we had plenty of captures but next to no re-sightings. Whether this is because we are comparing between different sites or between different age groups or between pre- and post-fire is something I will have to ponder on when I finish my analyses.
Every scientist is eagerly pounced upon by the ‘average person’ with questions like “What is the point of this?” or “Why put so much money into this?”, especially so when their study species is “… some random lizard in the middle of no-where..”. We hope to gather very basic biologically and ecologically relevant information without which any conservation planning for this species would be unfounded. Science tries to tease out a straight forward relationship from the inter-tangled mess that is real-world biology, so where people may often think “Species A eats species B. The End.” It is far more inter-connected. P. lineoocellata is most probably a predator to many insects, a host to many parasites, a snack to many bigger animals and may have some other ecologically relevant hobbies on the side (what a busy guy!).
Above the basics for conservation, these data will be used to improve the accuracy and reliability of Species Distribution Models (SDM). Most SDMs have relied on correlations between species occurrence and climatic data. This gives us an idea of what might happen to suitable habitat under different environmental change scenarios but the assumption was (and still is) often that said species can and will simply follow the suitable habitat. This project allows us to incorporate mechanistic data (i.e. data about the species and how it will respond biologically to change) into these models. The application of this is- you’ve probably guessed it- climate change predictions. If we are to act pre-emptively as conservationist we need predictive power- What is likely to happen in the future? And how will this detriment the survival of these species? This predictive power comes from activities such as SDM. These more intricate and skills-intensive work give us the opportunity to plan ahead to develop mitigation plans for different scenarios, brain storm possible social, financial and political barriers that may prevent effective conservation and target the more sensitive or problem species. This work on a seemingly random lizard is expensive and very laborious but is necessary. Every step in the process- from wandering through the veld in 40°C heat, to making observation, collecting data, analysing and interpreting the data and using it for a more applied purpose- builds on our knowledge base and improves the effectiveness of our conservation.
Ryan Daniels, SANBI, Cape Town
GDRI Work Package 4
Adams, R. a., & Thibault, K. M. (2006). Temporal resource partitioning by bats at water holes. Journal of Zoology, 270(3), 466–472. doi:10.1111/j.1469-7998.2006.00152.x
Goldberg, S. (2008). Reproductive cycle of the common rough-scaled lizard, Ichnotropis squamulosa (Squamata: Lacertidae) from southern Africa. Texas Journal of Science, 1–6. Retrieved from http://www.podarcis.eu/AS/Bibliografie/BIB_5453.pdf