Lab 1 Submission

Part A

Question A1

The species accumulation curves from the individual-based set is not the same as from the sample-based. I do not expect them to be the same shape. Sample-based increased in higher increments as more samples were taken. I suspect if the individual-based was taken to the same number of individual sampled, it would be of similar richness.

Question A2

I1 and I2 curves were shaped differently; S1 and S2 were also shaped differently. I would not expect them to be the same as the samples were random. Albeit, S1 and S2 was more similar than I1 and I2. This may be because S1 and S2 sampled a larger area.

Question A3

If organisms were aggregated, the sampled-based curve may be different. Each sample may overestimate one “organism” while leaving others out. I suspect the individual-based curve to be the same as it is a single random chance occurrence.

Part B

Question B1

Community C has the highest species richness.

Question B2

Yes, species richness (S) looks to be the same when the specnumber and rarefy rarefaction curves are compared. Below is the rarefaction curve for community B.

Question B3

The highest possible value of ED is 1. This means all the species have equal abundance. If the maximum value of 1/D is S, then at equal abundance, D and S cancel out in the evenness equation.

The lowest value of ED approaches 0. This only occurs if S (number of species) is significantly greater than 1/D. It is a mathematical impossibility to reach 0.

Question B4

##    SR  simp.inv simp.even     shan shan.even
## A   2  1.219512 0.6097561 0.325083 0.4689956
## B   9  4.219409 0.4688233 1.729214 0.7869992
## C  10 10.000000 1.0000000 2.302585 1.0000000
## D   7  7.000000 1.0000000 1.945910 1.0000000
## E   8  4.248646 0.5310808 1.691774 0.8135713

  1. Both communities A and B are diverse. Simpson’s evenness of B is lower than A, while Shannon’s evenness of A is lower than B. This is due to the different weight of common and rare species. While Simpson’s index weighs common species more, Shannon’s index weighs both equally. However, Shannon’s index is more suited to large communities.

  2. Both communities C and D are equally even. All indices agree. Community D, however, is lower in richness.

Question B5

After adding 1 hummingbird, S (species richness) increases by 1. e^H’ (shannon) increases by 0.21, and 1/D (simpson) increases by 0.02. Of these three figures, S (species richness) increased proportionally more. Thus, S is the most sensitive to rare species.

Question B6

Rare species sampled may only be passing through the sampling area (and do not inhabit the sampling area). If an index is very sensitive to rare species, diversity may be over-estimated; however, a sensitive index may be desirable if these rare species interact heavily with the sampling area.

Part C

Question C1

Except in perfectly even communities, rank-abundance curves decrease with rank similarly in communities A, B, and E. However, the curve is more linear in even communities (A, C, D, E), while it is more curved in the least even community (B).

Question C2

From a straight slope of the rank-abundance curve, we can tell which communities are more even (A, C, D, E) than others (B). From the data points, we can tell the species richness in the community (C, B, E, D, A), with C being the most diverse.