Infestation density and habitat suitability of tree girdling beetle, paranaleptes reticulata Thoms. (Coleoptera: Cerambycidae) in Eastern Tanzania
Loading...
Date
2024-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
Despite the increased rate of spread and infestation of the insect
pest, Paranaleptes Reticulata Thoms among government plantations
and other tree growers in Eastern Tanzania, there is limited
information on the infestation patterns and suitable habitat distribution
for P. reticulata. To provide this piece of information this study aimed
at assessing first, infestation density and severity of P. reticulata
across government plantation forests and community woodlots.
Modelling the current and potential future habitat distributions of the
P. reticulata in Eastern Tanzania. Data on presence of P. reticulata
and number of trees infested by P. reticulata were collected from 158
plots to count and measure trees infested by P. reticulata. Also, age,
diameter of infested trees and the occurrence coordinates were
recorded.
Non-parametric Kruskal-Wallis test was used to analyse if infestation
density and severity differed between agroecological zones and
species. Dunn's post hoc test was used to assess which sites and
species differed from each other in terms of infestation densities and
severity. Generalised linear mixed models (GLMMs) with a negative
binomial error distribution and plots as a random factor was used to to
assess the direction of associations between environmental variables
and the infestation density and severity of species. Ensemble species
distribution models combining presence records for P. reticulata and
potential environmental variables was used estimated habitat
suitability.
Results on infestation patterns revealed that infestation density (H =
83.95, df = 3, p < 0.001) and severity (H = 50.62, df = 3, p < 0.001)
differed between sites. Similarly, infestation density (H = 29.63, df =
2, p < 0.001) and severity (H = 29.63, df = 2, p < 0.001) differed
between species. GLMMs indicated that tree diameter, tree age, and
solar radiation were negatively associated with both infestation
density and severity, while wind was positively associated with both
infestation density and severity. Infestation density and extent of
severity were significantly higher for Corymbia citriodora and Eucalyptus tereticornis compared to the reference species
Commiphora Africana. Results on habitat suitability indicated that the
highly suitable habitat for P. reticulata would decrease significantly in
the year 2050 and 2090 under SSP126 and SSP585 scenarios.
The study concludes that exotic species are more prone to P.
reticulata infestations across sites compared to native species and
climatic variables play crucial in determining current and future habitat
suitability for P. reticulata. The study recommends age-, size-, and
species-specific preventive measures to reduce P. reticulata
infestation density and severity in Tanzania. Predictive maps could
also be used by managers, planners, and tree growers to strategize,
plan and making informed decision about the current and future
infestations status.
Description
MSc Dissertation
Keywords
Infestation severity, Ensemble models and Species distribution, Shared Socio-economic Pathways and Climatic scenarios