bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2021.10.11.463897

Combined effects of bird extinctions and introductions in oceanic islands: decreased functional diversity despite increased species richness

Soares, F. C.·de Lima, R. F.·Palmeirim, J. M.·Cardoso, P.·Rodrigues, A. S. L.
View original source ↗Export metadata ↓

Abstract

AimWe analyse the functional consequences of the changes in species composition resulting from extinctions and introductions on oceanic island bird assemblages. Specifically, we ask if introduced species have compensated the functional loss resulting from species extinctions. LocationSeventy-four oceanic islands (>100 km2) in the Atlantic, Pacific and Indian Oceans. Time periodLate Holocene. Major taxa studiedTerrestrial and freshwater bird species. MethodsWe compiled a species list per island (extinct and extant, native and introduced), and then compiled traits per species. We used single-trait analyses to assess the effects of past species extinctions and introductions on functional composition. Then, we used probabilistic hypervolumes in trait space to calculate functional richness and evenness of original versus present avifaunas of each island (and net change), and to estimate functional originality of extinct and introduced species. ResultsThe net effects of extinctions and introductions were: an increase in average species richness per island (alpha diversity), yet a decline in diversity across all islands (gamma diversity); an average increase in the prevalence of most functional traits (23 out of 35) yet an average decline functional richness and evenness, associated with the fact that extinct species were functionally more original (when compared to extant natives) than introduced species. Main conclusionsIntroduced species are on average offsetting (and even surpassing) the losses of extinct species per island in terms of species richness, and they are increasing the prevalence of most functional traits. However, they are not compensating the loss of functional richness due to extinctions. Current island bird assemblages are becoming functionally poorer, having lost original species and being composed of functionally more homogeneous species. This is likely to have cascading repercussions on the functioning of island ecosystems.

Source connections

Explore related subjects

ecologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Soares, F. C., de Lima, R. F., Palmeirim, J. M., Cardoso, P., Rodrigues, A. S. L.. 2021-10-12. Combined effects of bird extinctions and introductions in oceanic islands: decreased functional diversity despite increased species richness. https://doi.org/10.1101/2021.10.11.463897

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

A leaf-carbon economy model to explain the adaptive value of low vs. high leaf mass per area as a function of habitat productivity

Plant traits interact with environmental conditions to determine plant fitness. In particular, plant species with low leaf mass per area (LMA) are more common in high fertility soils and forest gaps, while plant species with high LMA are more common in low fertility soils and in shaded forest understories. It is not yet known why the adaptive value of LMA changes as a function of environmental productivity. We present a model for plant growth as a function of LMA and productivity. Our model relies on an empirically derived relationship between LMA and leaf lifespan. We are able to explain why species with lower LMA are successful in high productivity environments including environments with high availability of either light or soil nutrients, by showing that the LMA which maximizes growth rate decreases with increasing rate of carbon assimilation. We show that low LMA species are better at taking advantage of the 'high interest' environment of high productivity habitats by reinvesting assimilated carbon in new leaves and earning compound interest, while high LMA species grow more efficiently in the 'low interest' environment of low productivity habitats. This tradeoff sheds light on the adaptive value of LMA as it relates to environmental productivity.

ecology↗
bioRxiv2026

Species differentiate water uptake depths within a narrow vertical zone in temperate grasslands

Whether and under which conditions coexisting species in temperate grasslands differentiate their water uptake within the shallow soil layer they share is central to understanding hydrological niche differentiation in these ecosystems. In this field study, we quantified water uptake depth of 28 coexisting herbaceous species across 74 temperate grassland plots in three regions of Germany using oxygen stable isotopes and soil water content measured at multiple depths. Species consistently differed in water uptake depth across all regions, consistent with hydrological niche differentiation. This differentiation was largely confined to the upper 30 cm of soil and became stronger as overall soil moisture declined, with plants accessing water at greater depths in drier plots. In contrast, the vertical distribution of soil moisture was unrelated to either uptake depth or species differentiation. Despite pronounced species level variation, broad herbaceous functional classifications, including grasses versus forbs and fibrous versus taprooted species, showed substantial overlap in water uptake depth. Together, our results show that hydrological niche differentiation in temperate grasslands is expressed through fine scale differences among species within a shared shallow soil domain, becomes more pronounced under drier conditions, and is poorly captured by broad herbaceous functional classifications.

ecology↗
bioRxiv2026

Fungal-bacterial interactions enhance bacterial but constrain fungal resistance and recovery to extreme heat across soil moisture levels

Soil fungi and bacteria are key drivers of nutrient cycling and plant productivity in terrestrial ecosystems, yet their responses to climate extremes are rarely studied as interacting partners rather than in isolation. Moreover, it remains largely unknown how fungal-bacterial interactions regulate fungal and bacterial stability under climate extremes, particularly resistance (immediate responses to climate extremes) and recovery (responses after climate extremes cease). Here, we conducted a soil microcosm experiment with a bacterial species (Pseudomonas putida KT2440) paired with one of four Trichoderma species (T. hamatum, T. atroviride, T. koningiopsis, and T. harzianum). These fungal-bacterial pairs were then exposed to a 5-day heat event (40 {degrees}C/32 {degrees}C, day/night) followed by a 14-day recovery period (25 {degrees}C/17 {degrees}C, day/night), at two soil moisture levels (30% and 5% gravimetric water content). Our results show that fungal-bacterial interactions asymmetrically affect fungal and bacterial responses to extreme heat. Trichoderma species facilitated the resistance and recovery of P. putida density (CFUs) to extreme heat, whereas P. putida constrained the resistance and recovery of fungal biomass (ergosterol) to extreme heat, regardless of soil moisture conditions. Moreover, faster-growing Trichoderma species were associated with greater facilitation of bacterial resistance and recovery. Bacterial density also covaried positively with fungal biomass during heat stress under both soil moisture conditions, suggesting that net fungal facilitation enhances bacterial persistence under extreme heat. Together, our findings reveal that fungal-bacterial interactions can stabilize one microbial partner while increasing the vulnerability of the other, highlighting the contrasting consequences of biotic interactions under climate extremes.

ecology↗