Spatiotemporal pattern of specialization of sunbird-plant networks on Mt. Cameroon

Abstract

Differences in interaction specializations between nectarivorous birds and plants across continents serve as common examples of evolutionary trajectory specificity. While New World hummingbird-plant networks have been extensively studied and are considered highly specialized, knowledge on the network specialization of their Old World counterparts, sunbirds (Nectariniidae), remains limited. A few studies from tropical Africa indicate that sunbird-plant networks are rather generalized. Unfortunately, these studies are limited to dry seasons and high elevations at the tree line, environments where niche-based hypotheses also often predict lower resource partitioning. In our study, we explored the specialization of sunbird-plant networks and their spatiotemporal variability on Mt. Cameroon (Cameroon). Using a combination of automatic video recordings and personal observations, we constructed eight comprehensive sunbird-plant networks in four forest types at different elevations in both the dry and wet seasons. As reported in previous studies, the montane forest plants, birds and whole networks were highly generalized. Nevertheless, we observed a much higher specialization in forests at lower elevations. Except at the lowest altitude, the wet season was also characterized by higher specialization. While less specialized flowering trees dominated in the dry season networks, more specialized herbs and shrubs were visited by birds during the wet season. As our findings do not support the generally accepted assumption that Old World bird-plant networks are rather generalized, we need further studies to understand the differences in bird-plant specializations on individual continents.

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Oecologia (2022) 199:885–896
https://doi.org/10.1007/s00442-022-05234-4
PLANT-MICROBE-ANIMAL INTERACTIONS – ORIGINAL RESEARCH
Spatiotemporal pattern ofspecialization ofsunbird‑plant networks
onMt. Cameroon
ŠtěpánJaneček1 · KryštofChmel1· JiříMlíkovský1· GuillermoUceda‑Gómez1· PetraJanečková1·
NestoralTajaochaFominka1,2· MarcusMokakeNjie1,3· FrancisLumaEwome1
Received: 11 August 2021 / Accepted: 26 July 2022 / Published online: 10 August 2022
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2022
Abstract
Differences in interaction specializations between nectarivorous birds and plants across continents serve as common examples
of evolutionary trajectory specificity. While New World hummingbird-plant networks have been extensively studied and
are considered highly specialized, knowledge on the network specialization of their Old World counterparts, sunbirds (Nec-
tariniidae), remains limited. A few studies from tropical Africa indicate that sunbird-plant networks are rather generalized.
Unfortunately, these studies are limited to dry seasons and high elevations at the tree line, environments where niche-based
hypotheses also often predict lower resource partitioning. In our study, we explored the specialization of sunbird-plant net-
works and their spatiotemporal variability on Mt. Cameroon (Cameroon). Using a combination of automatic video recordings
and personal observations, we constructed eight comprehensive sunbird-plant networks in four forest types at different eleva-
tions in both the dry and wet seasons. As reported in previous studies, the montane forest plants, birds and whole networks
were highly generalized. Nevertheless, we observed a much higher specialization in forests at lower elevations. Except at
the lowest altitude, the wet season was also characterized by higher specialization. While less specialized flowering trees
dominated in the dry season networks, more specialized herbs and shrubs were visited by birds during the wet season. As
our findings do not support the generally accepted assumption that Old World bird-plant networks are rather generalized, we
need further studies to understand the differences in bird-plant specializations on individual continents.
Keywords Bird pollination· Ecological network· Elevation· Sunbird· Seasonality
Introduction
Specialization of plant-pollinator networks is a fundamental
ecosystem characteristic. Knowledge on this specialization
and how it is affected by various environmental conditions is
significant from many points of view. It is important not only
for conservation purposes (e.g., for estimating the extinction
risk of individual organisms, Vanbergen etal. 2017) and for
predicting the effects of future climate changes on plant-
pollinator communities (Hoiss etal. 2015) but also for a gen-
eral understanding of evolutionary and speciation processes
(Ramírez etal. 2011).
Specialization in plant-pollinator networks reflects
resource (niche) partitioning among species, which can be
driven by the tendency of plants and pollinators to use only
a subset of potential resources and by interplant or inter-
pollinator interactions such as competition (Blüthgen etal.
2006). Some of the most studied networks are those among
plants and nectarivorous birds. Nevertheless, whereas
researchers have often targeted hummingbird-plant interac-
tions, networks including other groups of nectarivorous birds
remain underexplored. A few studies on African sunbird-
plant networks indicate that they are less specialized than
hummingbird-plant networks (Zanata etal. 2017; Nsor etal.
2019). Nevertheless, other studies revealed many similarities
that should result in a similar degree of specialization. For
Communicated by David M Watson .
* Štěpán Janeček
stepan.janecek@natur.cuni.cz
1 Department ofEcology, Faculty ofScience, Charles
University, Viničná 7, 12844Prague2, CzechRepublic
2 Department ofZoology andAnimal Physiology, Faculty
ofScience, University ofBuea, P.O. Box63, Buea,
Cameroon
3 National Forestry School, Mbalmayo, P.O. Box69, Yaounde,
Cameroon
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