Self-similar patterns of nature: insect diversity at local to global scales
Bland J. Finlay, Jeremy A. Thomas, George C. McGavin, Tom Fenchel and Ralph T. Clarke
Blog Author: Sebastian Botero
Bland J. Finlay
Currently an associate professor of microbial ecology at theSchool of Biological and Chemical Sciencesof London Queen Mary University.
His research interests are (taken from https://www.qmul.ac.uk/sbcs/staff/blandjfinlayfrs.html):
· Ecology and physiology of free-living Protozoa
· Dimensions and dynamics of biodiversity at the microbial level
· Rationalizing biological and habitat complexity
· Characterizing the dimensions of biodiversity across spatial scales and in different biogeographical regions
Revealing new and previously unexplored ‘patterns of nature’, and their ecological significance
Exploiting simple techniques of data handling to yield self-similar and other natural patterns that can be used for interpolation – e.g. estimating species richness at different spatial scales - with implications for conservation practices.
Background:
Insects are undoubtably the most diverse group of animals on earth, with around 750.000 described species and estimates of total species richness ranging between 4 to 10 million. Given this huge diversity, simple macroecological and biogeographical patterns might by difficult to grasp. Nonetheless, the description and understanding these patterns might reveal patterns among scales leading to extrapolation and interpolation for incompletely sampled areas (which comprise most of the world). This need is even more urgent as the insects also appear to be suffering high rates of extinctions under the current environmental change.
Methods:
The authors compiled data on insect species richness and size for 176 families from several inventories, regional and global lists. This resulted in lists of insect families, their size and species richness at several scales, from few hectares to the entire biosphere (including a global sample of around 80% of the currently described species). Using this list, the authors analyzed the rank abundance distribution of species richness per family, size-frequency distribution and the relation between local:world species ratio and size at all the available scales. Finally, area-species curves and relation of species richness for each family among scales are analyzed.
Results:
- At all scales, rank-species richness per family curves show the same shape. Null models indicate that this is the result of local faunas being a random sample of regional and global faunas.
- Interestingly, the size distribution of insects presents four peaks in number of species, which coincide very well among spatial scales when scaled as proportion of species instead of absolute richness.
- At local to regional scales, the smaller species tend to represent a higher portion of the overall diversity, indicating wider distribution of these groups. It is argued that this pattern results from higher abundances of smaller species which favor their dispersal probability.
- The observation mentioned above is further supported by flatter species-area curves for smaller species.
- Finally, it is shown that species richness in each family is correlated with richness at increasing spatial scales. For example, the number of species in for each family in the UK is correlated with the number of species in North America.
Discussion:
- Self-similar patterns across scales independently of the geographic area suggest that some fundamental characteristics of dispersal, speciation and evolutionary divergence are common to most, if not all insect species.
- This information can be used to extrapolate species richness or other community properties among scales, which can prove very helpful in understanding and assessing the impact of human activities on insect diversity.
- More data from diverse ecosystem is needed to further corroborate the observed patterns.
- Self-similarity might appear in other diverse groups.
Comments:
- The size frequency distribution is different from what we have seen for other groups, including the results from May (1978). I was expecting more discussion about the mechanisms behind this pattern.
- Another unexpected result for me is the inferred higher dispersal ability for smaller animals. I always thought that in general the bigger the animal, the better dispersal capacities, probably very mammal biased.
- Finally, I think it would have been very interesting what the results look like with data from tropical areas, specially at the local scale.
I would guess that their dispersal ability does not stem from their size but from the large quantity of individuals. Similiar to rodents having such incredible dispersal abilities. I also agree I would have expected more about the mechanism behind the results.
ReplyDeleteI agree with Sebastian. I would really enjoy this paper if it talks more about the mechanisms behind all of this. I was also confused about dispersal ability vs body size. When we talk about dispersal ability, are we talking about dispersal of the whole population or average of an individual?
ReplyDeleteI agree with everyone else about how the paper would have been improved with discussion about the mechanisms behind the observed patterns. I was a little surprised that the current extinction rate of insects is higher than that of birds and plants. This will directly affect bird populations (since they eat insects) and plant populations (since many insects pollinate/eat them). It'll be interesting to see what happens in the next few decades.
ReplyDeleteIt took me a little while to understand self-similar size-frequency. Overall, it is an interesting paper to see the global insect diversity assessment based on their body size and distribution. I am curious about the smaller sized insects would have a better advantage for wind transportation that would allow them to disperse better. I am not an entomologist so I don't know how much it would matter but ecologically, they should have preferred suitable habitat for each species. Very interesting robust graphs are shown here. More of these kinds of work would allow us to monitor biological process especially the insect, plant, and parasites.
ReplyDeleteSeconding everyone's comments about more discussion as to the mechanisms behind these trends. I think the plots are very interesting and well made. I do have to wonder if trends in insects, especially flying ones, can and should be compared to mammalian trends seen with body size, range size, and latitudinal gradients. Living requirements and life habit is so different between the two animal groups that I'm not sure if comparing to mammalian or even reptilian trends is a good idea.
ReplyDeleteAlso curious why the size-richness figures produced patterns that are different that what we've talked about. Not sure if we've discussed this, but why is diversity so much lower in Europe?
ReplyDeleteIt's nice to change from talking about plant and fossils to insects. It was interesting find out that when reviewed, the data showed only 3 dominate species when it came to size frequency distributions. I figured it would have been more. I also really enjoyed reading about how body sizes correlated with the species area curve. This paper held a lot of interesting data analyses that made it a little easier to stay interested while reading. Overall it wasn't too bad of a read.
ReplyDelete