4.2.1 Global distribution
Over half (59.3%) of all frugivore tracking studies reviewed here were
in tropical regions (between 23.436°N and 23.436°S; Fig 2). A further
14.2% were from the sub-tropics and 26.5% were from the southern and
northern temperate zones. This reflects latitudinal patterns of higher
species richness in tropical compared to temperate regions. However,
this pattern was not seen in studies that calculated seed dispersal
distances, where only 31% of studies were in tropical regions, and does
not reflect difference in animal mediated seed dispersal globally; up to
60 % of temperate plants rely on animal dispersal compared to 90 % of
tropical plants (Howe & Smallwood, 1982; Gentry, 1988). This suggests
that in the tropics we see a lack of seed dispersal studies using animal
movement data, potentially because fieldwork locations and dense forests
provide challenges to fieldwork and transmitters (Kays et al, 2011;
Monsieurs et al, 2017). However, the uptake of solar powered tags,
improvement in battery capacity and remote downloading capabilities may
soon rectify this (Byers et al, 2017; Fischer et al, 2018). Our
data also suggest that many regions have yet to be explored for the
study of frugivore movement, for example Eastern Europe, Central &
Northern Africa, Central Asia and much of North America lack tracking
studies (Figure 2).
Sites where multiple studies have been conducted tended to be in
protected areas and/ or at key field stations. In total, 172 different
locations were used for these tracking studies, with almost two thirds
(59%) in protected areas, with clustering of multiple studies at
long-term research stations (Blanco et al, 2020). This is both a
benefit and a limitation; on the one hand, highly studied sites become
hotspots for research, with multiple taxa studied in a single location
and often with longitudinal datasets (Stouffer, 2020). This provides
information on how multiple taxa respond to the same landscape changes
and how patterns may differ amongst species. Alternatively,
concentrating multiple studies in a few locations means that we make
inferences from a handful of intensely studied sites, and lack broader
knowledge from diverse locations and landscapes. Most studies we
reviewed were in protected areas, but these represent < 10%
of terrestrial land surface area, suggesting that we need further
studies outside parks and reserves as well as comparative studies in
protected areas and neighbouring disturbed habitats to effectively
survey a representative sample of habitats