Download Viva Abstract_Perpetra Akite

Spatial and matrix influences on the biogeography of insect taxa in forest fragments in
central Uganda
Perpetra Akite
Abstract
How best to manage forest patches, mitigate the consequences of forest fragmentation, and enable
landscape permeability are key questions facing conservation scientists and managers. As tropical forests
become increasingly fragmented, there is a reduction in interior forest habitats, increase in edge habitats,
and reduction in connectivity. Consequently, it has become increasingly apparent that understanding how
species are affected by fragmentation requires information on their responses to all components of the
landscape, i.e. forest patches, remaining continuous forest, and the intervening matrix. However, very
little is known of how faunal communities and in particular insect assemblages utilize resources within
the patch-matrix landscape. The subsequent impact of forest fragmentation on species turnover across
spatial and temporal scales also remains largely unclear. The main objective of this study was to assess
patterns of diversity of three insect taxa and their relation to habitat heterogeneity, disturbance gradient
and how anthropogenic impacts may be altering these patterns. A combination of butterflies, moths and
grasshoppers were studied as model indicators to describe patterns of diversity and distribution across the
temporal, vertical and spatial scales in three forest reserves; Mabira (largely stable and recovering from
past encroachment, albeit with minor illegal logging, but disturbed at the edges), Zika and Mpanga
(relatively undisturbed and unchanged internally, but with substantially altered matrix), all in central
Uganda. All together, 25156 individuals (327 species) of butterflies, 1131 individuals (41 species) of
silkmoths, 1564 individuals (44 species) of hawkmoths and 2173 individuals (49 species) of grasshoppers
were recorded across the forests and their surrounding matrix habitats. Overall, there was a marked
decline in richness and abundance of species over time, even within relatively stable forests. The temporal
decline was most drastic for forest-dependent species, while generalist species mostly showed the reverse
trend. This change was more evident in the smallest Zika forest. There was a marked variation in species
distribution within the vertical strata; more specialists were found in the canopy, despite a higher number
of individuals in the understorey. This study also recorded a general decline in richness and abundance of
species along a land-use gradient from mature forest to home gardens, with forest specialist species
showing severe declines, and several species only restricted to the mature forests. The patterns were
consistent across the different ecologically-distinct insect taxanomic groups. These findings together with
similar patterns reported for other taxa in similar habitat settings indicate a worrying reduction in the
capacity of protected forests to main biodiversity. Since protected forests are ecologically linked to their
surrounding habitats, failure to stem broad-scale loss and degradation of these habitats will consequently
increase the likelihood of serious biodiversity declines and subsequent extinction.
Supervisors:
Assoc. Prof. R.J. Telford
Assoc. Prof. A.M. Akol
Prof. Emeritus. C.H.F. Rowell