PAPER 16: Species Number, Species Abundance and Body Length Relationship of Arboreal Beetles in Bornean Lowland Rain Forest Trees (1988)
D. R. Morse, N. E. Stork, and J. H. Lawton
Blog author: Lam Le
Blurb author: Alistair Evans
-Associate Professor at Monash University
-Head of Evolutionary Morphology Laboratory at Monash University
-Area of research: evolution, development and function of teeth of mammals
Paper author:
D. R. Morse
(couldn’t find much information on this author)
N. E. Stork
-Deputy Head of School of Environment at Griffith University, Australia
-Head of Department of Resource Management and Geography at University of Melbourne, Australia
-Area of research: biodiversity, conservation biology, taxonomy, ecology, ants
J. H. Lawton
-PhD at University of Durham, 1969
-Founder and Director of NERC Center for Population Biology at Imperial College, Silwood Park.
-Chairman of the Royal Commission on Environment Pollution from 1 April 2005
-Japan Prizefor Science and Technology for Conservation of Biodiversity in 2004 "for observational, experimental and theoretical achievements for the scientific understanding and conservation of Biodiversity"
-Area of research: population dynamics and biodiversity of birds and insects, with emphasis on the impact of global environmental change on wild plants and animals.
Main Question: Is there a relationship between number of species, species abundance and body size?
Background:
The relationship between pairs of variable number of species, species abundance, and body size had been considered, but R. M. May recognized that these 3 variables should be interrelated. The data for explanation of this was lacking. To address this, the authors measured the number of species, species abundance and body length of beetle assemblages in Bornean lowland rainforest trees.
Assumptions:
-The purpose is to establish what the patterns look like, not to develop theories to explain the patterns
-Data are not ideal, but are the best currently available
-There might be bias in sampling of Coleoptera
Methods:
-Samples of arthropods were collected by fogging the canopy of trees with synthetic pyrethroid insecticide in lowland rain forest near Bukit Sulang, Brunei. Ten trees were chosen for sampling.
-Insects were sorted into orders and species. Coleoptera were assigned into herbivores, predators, scavengers, fungivores.
-Body length was used as a measure of size. Length is easier to measure than weight. Length and weight are highly correlated.
-Mean body lengths were estimated from a max sample of 10 specimens per species and grouped into a series of length classes arranged on a log scale.
Results:
-The Coleoptera comprise majority of small arthropods but lack in larger sizes.
-The number of rare species, 58% species represented by single individuals. Linear relationships between species-rank and species abundance on double log scale have different slopes for different species.
-Number of species vs body length class: the most species rich size classes are in different positions for each guild and the shapes of distributions are different.
-There are no consistent relationships between size and population abundances.
-Distribution for individual guilds tend to be skewed relative to total distributions, with modes in different body length classes.
-When combining all 3 variables into 3D plots for all beetles and individual guilds, the full surface is smooth with small ridges (different guilds contribute differentially to each ridge)
Discussion:
-Advantage of this study:beetles represent major proportions of 4 of the guilds of arthropods most closely associated with trees, and represent feeding habits of arthropod fauna in Brunei rain forest.
-Disadvantage of this study:lack of generality, cannot use this study to infer to the whole arthropod communities
-Insecticide fogging is effective in collecting adult beetle samples. Adult beetles varied little in size within species. Beetle larvae looked different than adults, found in different habitats, and were excluded from analysis.
-No consistent linear relationship between population density and body length was found. The added dispersal/flight ability reduces population densities.
-Fail to locate the mode in plots of species vs abundance distribution.
-Species vs body length and total number of individuals vs body length plots were similar to previous studies. Using data for Coleoptera produced steeper decline in total nuber of individuals as body size increases than in sample of all arthropods.
-Generate first 3D graph of number of species, body lengths and population abundances.
Comments:
-This paper is very thorough. The references to other papers make it a little bit hard to read and follow through with the idea. I have trouble understanding 3D plots and the ridges, so I might need more explanation on this in our next class.
So that was a ridiculous number of dead bugs out of only so many trees. I sort of wonder if there was a local extinction after this study and if the population dynamics would change after removing soooooo many bugs. Either way, it was neat that they tried plotting the three variables together in a 3D plot and also neat that they distinguished that they did not want to make interpretations, just to model the bugs.
ReplyDeleteAs we add more variables to look at the community level patterns, the most influential variables will be filtered in to show more realistic patterns. I wonder if someone has done that in the northern part of the hemisphere to compare the difference to select and text more influential patterns. We could go around the sampling bias by choosing the right compatible habitats by selecting similar characters in the area. I wonder what happens to the Beatle communities after the fire. I bet the community structures change even with the body size when forest resets itself. The 3D plotting data point (multivariate) generates a graph that shows a shape that unique to that dataset. These 3Ds can be compared against other 3D graphs that make using different plot point values. Each shape indicates the correlation among variables.
ReplyDeletenot text, it is test.
DeleteI was surprised that they did not find a pattern in population density and body size among them. Due to the density and variety of trees in the tropical forests, I wonder if you wouldn't see a correlation between body size and population density in a temperate forest where there may be greater competition for resources.
ReplyDeleteA sampling of 10 trees seemed small to me, so I was pretty amazed at the sheer number of critters that fell out. I also thought the 3D model was neat. I'm curious how subsequent research further explored this relationship.
ReplyDeleteI think the authors were very thorough with the variation of questions that they tried to answer. They seemed to try and think of the possible combinations that could be tested with the data and then tested them. 10 trees does seem like a small amount of sampling data, especially as it didn't seem as the sampling procedure was labor or time intensive. It also seemed odd to me that they brought diet into results but didn't talk about it in the discussion. It is interesting to look at body size at other groups of animals other than mammals.
ReplyDeleteAlthough I like reading about mammals, it is nice to learn something about insect ecology. I was surprised by the amount of individuals and specially by the amount of species in just ten trees. The diversity is even more impressive if we take into account the fact that for most species they just had a single individual so probably it should be much higher (unless their "tourist" hypothesis is correct). I didn´t understand well why they said they didn´t discover the mode of the distribution, is it because most species are represented by one individual?
ReplyDeleteThe rainforest is truly an incredible biome. It is impossible to make someone understand how many organisms (and how many different species) live there without handing them a plane ticket and telling them to go look for themselves. As Kate said in class, there may be >1 million extant species of insect that scientists have yet to describe. It's simply extraordinary.
ReplyDeleteSince this study was a first stab at understanding the interrelatedness of several variables, I wonder how much more we know now. Did these authors go on to focus on taxa other than Coleoptera?
I was astonished when I read their sampling method. Spraying pesticide in a tropical forest seems too dangerous to me. The wind could carry that pesticide to other trees as well, and it definitely didn't just kill beetles as they mention. I just hope they did publish their results from the other arthropods sampled in that area, because if beetles are just a fraction of the insects collected, there were thousands of other animals there too. Are now other methods for sampling canopy communities? I have tried light tramps before to look for canopy jewel beetles too, but I don't think we got a representative sample of all canopy beetles.
ReplyDeleteAlso I wonder, what is the fractal nature of plant surfaces?
Normally I hate reading about insects, but this is a really cool article/ write up about beetles. I feel like their methods was short (but that’s due to the fact they followed another procedure in another article... I would have liked to read what they did) and the sample size seems small to me. I feel like if they were only going to use 10 trees, they could have at least used 10 trees from 5 different areas or something like that. Maybe the sample size was too small and if they had a bigger sample size they would have had different if not better results. Also, I think figure 7 is the coolest graph I have ever seen in my life.
ReplyDelete