Report – BS2001 – Abundance of Mistletoes

BS2001, 2000-04-05

Study of Abundance of Mistletoe In Eucalyptus Trees At James Cook University

Abstract

The dependence of parasitic plants on other plants varies greatly, for example, mistletoes depend on their host only for minerals and water though they have chlorophyll but lack roots. The occurrence of leafy or true mistletoe is widely spread all over the world, but especially trees in warm climates (Agrios, 1997).

The study of distribution of mistletoe in the canopy of Eucalyptus spp. and Acacia spp. were conducted around James Cook University, Townsville, in tropical north Queensland. Observations were made of environmental factors determining the zonation patterns and the relationship between the two sample areas.

Results show mistletoe is more abundant inside the ring road than on the outside. The effects of plants and evidence of other impacts are discussed.

Introduction

To overseas visitors the Eucalyptus spp. are as Australian as Koalas and Kangaroos. Eucalyptus spp. dominates Australian landscapes, except for the rainforests and the arid interior. Despite the present-day dominance of Eucalyptus spp., little is known about their evolutionary history from the fossil record. It is thought, however, that Eucalyptus spp. is an ancient Australian group that has increased in dominance relatively recently as the climate developed a marked dry season, and fires became more frequent (Knox et al. 1999).

In excess of 2500 species of higher plants are parasitic. The most common parasite associated with Eucalyptus spp. that effects their growth is the mistletoe family Loranthaceae. This family uses inorganic material to photosynthesise, yet they are totally dependent on other plants till death do them part (Penfold et al. 1961). They depend on their host only for minerals and water though they have chlorophyll but lack roots.

Distribution is generally done by either seed discharge, sticking to the feet or feathers of birds or even spread by the faeces of the birds (Raven et. al. 1999). Mistletoe distribution has been seen to differ dramatically between cultivated and non-cultivated areas because of differences in the availability of nutrients, water, sunlight and protection. So the distribution of mistletoe is therefor apparently indicative the distribution of birds. This study was to find out if the distribution of mistletoe varies between the two sites with differing habitats.

Aims:

1 – Determine whether the distribution of mistletoe is the same at two sites with obvious habitat differences (e.g. one inside and one outside James Cook University campus the ring road)

2 – Test whether the mistletoe distributions are random at either site? If they are not, what type of spatial distribution patterns do they appear to have?

Methods

This study were conducted around James Cook University, Townsville, in tropical north Queensland, (146.80 E, 19.30 S).

On a map over James Cook University, 25m2 quadrates were marked out (Appendix 1).

The area was then divided into cultivated and non-cultivated area by defining cultivated as the area within the ring road, excluding the construction site in the northern end and the southern end due to that being non-cultivated.

The western part of the campus was excluded from both the cultivated and the non-cultivated area though it was considered inaccessible and misleading.

The area outside the ring road was defined as non-cultivated.

Each area was numbered and coloured as follows,

– Cultivated area – PINK, 1 – 157

– Non-cultivated area – YELLOW, 1 – 108

On a map over James Cook University, a grid pattern, divided into 25m2 quadrates, where placed (see Appendix 1). A building site (A) and a non-cultivated area (B) inside the ring road were not included. Outside the ring road, the halls of residents ground (C) and the fenced aquaculture facilities (D) were also excluded.

The 50 randomly selected grid squares were each previously decided that the tree far most to the southwestern corner of the square should be recorded of mistletoe abundance.

Results

Data analysis

Homogeneity test – X2 inside: 42.000, X2 outside: 65.840

Goodness of fit indicated that the H0 should be rejected, and therefor a VMR test was done.

It showed that there was a significant difference between the cultivated and non-cultivated areas.

Inside: (X2 (a = 0.05, d.f. = 22) = 42.000

Outside: (X2 (a = 0.05, d.f. = 7) = 65.840

Fig 1. Total number of mistletoes inside and outside the ring road at James Cook University.

To see if the mistletoes were randomly distributed in each site VMR was used. The data showed significant aggregated value of 12.2, inside the ring road. Outside the ring road the distribution was aggregated as well but not as much as inside. VMRoutside: 3.4.

Discussion

There were significantly more mistletoes inside the ring road than outside. Inside of the ring road the mistletoes where evenly distributed while outside they where aggregated.

Inside the ring road the area of cultivated land is under constant artificial management, it is regularly watered, especially in the dry season, and taken care of by ground staff all year. The area is also given nutrients, protection from competition due to ground staff take away all the seedlings by mowing the lawn. The area is also free from shrubs and other vegetation that means that the trees and therefore the mistletoes get more sunlight. The mistletoe is a light-loving plant often found in the vicinity of cultivation and specially in well-watered areas (Blakely, 1922). A significant aggregated pattern was shown inside the ring road. The lack of vegetation tends to enhance the distribution of the mistletoe this might be due to the increased ability for birds to move about between the trees. This might also result in larger amount of nests inside the ring road due to the birds get fed by or the access of food from students and therefore attracted to the cultivated area.

The aggregated pattern outside the ring road was not as significant as inside this might enhance competition in both finding food, good nesting places. The access of water, nutrients are reduced and the outside is also a victim of occasional fires which also decrease the presence of mistletoe (Penfold et al. 1961). The birds may tend to live outside the ring road due to the noisy students and the Bludgers’ Pub.

References

Agrios, G. N. (1997). Plant Pathology, 4 ed., Academic Press Limited, London

Blakely, W. F. (1922-5). The Loranthaceae of Australia.Proc. Linn. Soc. N.S.W

Knox, B., Ladiges, P. and Evans, B. (1999) Biology. McGraw-Hill Book Company Australia Pty Limited, Roseville.

Penfold, A. R. & Willis, J.L. (1961). The Eucalypts, Interscience Publishers, Inc. New York.

Raven, P. H., Evert R. F., Eichhorn, S. E. (1999) Biology of plants, 6 ed., W. H. Freeman and Company, Worth Publisher, New York

Acknowledgements

I like to thank the following people for helping me out with the sampling for this study:

Fleiss, Steven

Hayllar, Rebecca

Kinna, Belinda

Robertson, Catherine

Seavons, Clint

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