State of the Greater Fundy Ecosystem

GREATER FUNDY ECOSYSTEM RESEARCH PROJECT

UNB Faculty of Forestry and Environmental Management

State of the Greater Fundy Ecosystem

Species Level Diversity of Lepidoptera
in Forested Ecosystems

Anthony W. Thomas1 and Douglas Clay2
1 Canadian Forest Service - Atlantic Forestry Centre,
Fredericton, N.B. E3B 5P7
2 Fundy National Park, P.O. Box 40, Alma, N.B. E0A 1B0

Over 75% of the world's biodiversity (species level) consists of insects and their allies. Of the insects attacking plants, 95% are leaf-chewers and most of these are lepidoptera (butterfly and moth caterpillars). Lepidoptera, with their great abundances in both number of species and number of individuals, play a key role in forest ecosystem dynamics. As the major converter of plant biomass to animal proteins and fats, lepidoptera drive the flow of energy that allows for the high biodiversity seen in forest ecosystems. Lepidoptera are a high quality food item for predators such as birds, small mammals (terrestrial, arboreal, and aerial), amphibians and reptiles. Almost all of the forest bird species are totally dependent on lepidoptera for the rearing of young. Because lepidoptera overwinter, they form a critical food reservoir for resident small mammals and birds that remain active during Canada's winter. The variation in size of lepidoptera and their exploitation of every conceivable feeding niche allows for the high diversity of bird species in our forests. All of the large predators that exploit small vertebrates are ultimately dependent on the lepidoptera which in turn are dependent on the flora. However, the presence of a diverse flora does not in itself guarantee the presence of a diverse lepidoptera fauna. The presence of a diverse lepidoptera fauna allows for the presence of a diverse bird fauna.

The moth Panthea pallescens (Photo: A. Thomas)

Moth trap at Wolfe Lake, Fundy NP (Photo: A. Thomas)

GOAL

The study was started in 1994 in the relatively undisturbed forests of Fundy National Park (Fundy NP) to gather baseline data on the diversity of lepidoptera to use as a yardstick to measure the impact of anthropological perturbations on forested ecosystems in the Fundy Model Forest (FMF).

RESULTS TO DATE

A review of the butterfly species in Fundy NP has been produced (Thomas, 1997). In general, butterfly species are few and their numbers low. They are of minor importance in the forest ecosystem. The other group of lepidoptera, moths, are both numerous in species and individuals and are a critical component of the forest ecosystem. To date, the only data analyzed was collected at the Wolfe Lake site. Effort was directed at 15 families containing the larger moths, the macro-moths. In the 3-year study (1994-96) 45,324 moths in 514 species were recorded. There are probably a similar number of species in the micro-moth families. It is worth noting that the 45,000 adult moths represent the 'tip-of-the-iceberg' in terms of biomass. In terms of population dynamics, the adult moth stage represents the lowest number of individuals. Moth caterpillars outnumber the adults by about 100:1. It is the caterpillar stage that does the energy conversion and forms the basis of the food-chain.

The approach taken for determining anthropogenic perturbations is to compare species richness and patterns of abundance in undisturbed forests with those in perturbed forests. To this end, the pattern of species abundances in a FNP forest is presented here as a first step in the process. The bars in Figure 1 show the abundance pattern, for the first 50 classes, for the 1994 Wolfe Lake data. A hollow curve with a high number of rare species and a long tail of increasingly common species (note that one species had 1,253 individuals) is typical of the pattern seen for a moth community in a stable ecosystem. Also plotted in Figure 1, as a line, is the logarithmic series distribution for the two variables. Note the closeness of the fit between the observed frequencies and the model.

Some life stage (ova, larvae, pupae, imagines) of each of the 401 species is present during the entire year. However, in the temperate climate of New Brunswick there is a marked seasonality in the appearance of the adult moths. Figure 2 shows the peak occurrence of species occurred during weeks 26-28 (26 June - 16 July) in 1994. No samples were collected during weeks 36, 37, 38.

Figure 1. Frequency distribution of macro-moths, with different numbers of
individuals, from light-trap catches at Wolfe Lake, Fundy NP, 1994 (bars);
first 50 classes only. The logarithmic series distribution for the two variables
is shown as a solid line.

Figure 2. Seasonality of adult moths, as determined from light-trap catches,
for the Wolfe Lake site in 1994. Week 28 = 3-9 July. No collections were
made before week 19, during weeks 36-38, and after week 39.

Polyphemus moth (Photo: A. Thomas)

Close-up of Polyphemus moth (Photo: A. Thomas)

Further reading:

Edsall, J. and D. Clay. 1994. Preliminary survey of Lepidoptera in Fundy National Park (including a checklist of species recorded in 1993). Unpublished manuscript of Parks Canada, Alma, N.B. Res. Notes of Fundy Nat. Park. No. 94-06.

Thomas, A.W. 1997. Status of butterflies of Fundy National Park and its greater ecosystem. In: D. Clay (ed.) Resources of Fundy National Park: A primer of ecosystem studies.Part II. Chapter III. Pks. Can. Eco. Sci. Rev. Rept. No.4.

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