j.g. pausas' blog

Hummingbirds are among the most iconic birds of America, especially abundant in the tropics. They are very important pollinators (nectar feeders), thus their abundance and distribution are likely to affect hummingbird-pollinated plants, many of which are endemic or endangered. A recent review in western United States [1] suggests that most hummingbird species respond positively to wild or prescribed fire and thus, for the conservation of these emblematic birds, it is important to promote landscape mosaics, with early and mid postfire successional habitats, together with forest patches.

Here is a video by Contreras-Martínez et al. on hummingbirds and wildfires in Sierra de Manantlán Biosphere Reserve, Mexico [2]. The video is in Spanish; hummingbirds are ‘colibríes’ or ‘picaflores’

Créditos del vídeo:
Filmación y Edición: Carlos Armando Pacheco Contreras (Vidacinema)
Productor: Sarahy Contreras Martínez
Guión: Sarahy Contreras Martínez, Carlos Armando Pacheco Contreras & Oscar Cárdenas Hernández
Narración: Cesar Híjar Tejada
Investigación Científica: Sarahy Contreras Martínez (Colibríes) & Enrique Jardel Peláez (Fuego)
Música Original: Erick Ríos Vázquez
Mezcla de audio: Sognare Estudios
Also available at: https://www.facebook.com/watch/?v=869506306897201

References
[1] Alexander JD, Williams EJ, Gillespie CR, Contreras-Martínez S & Finch DM. 2020. Effects of restoration and fire on habitats and populations of western hummingbirds: A literature review. Gen. Tech. Rep. RMRS-GTR-408. Fort Collins, CO, USDA, https://www.fs.usda.gov/treesearch/pubs/59664

[2] Pausas JG 2016. Flammable Mexico. Internat. J. Wildland Fire 25: 711-713. [doi | pdf ]

[3] Other related videos: Burning for biodiversity | Fire & the Florida scrub | La huella del fuego | Fish & fire | 

[4] Other post on fire & fauna | fire & pollination | fire & Mexico |

In ecosystems with a dens vegetation, wildfires open the canopy and create an environment with more light and less competition. In such postfire conditions there is an increase in flowers, and thus, flower visitors are also likely to increase. In a recent article [1] we performed a meta-analysis to specifically evaluate the effect of fire (prescribed and wildfires) on pollinators from 65 studies in 21 countries across de globe. The overall effect of fire on abundance and richness of pollinators across all studies was positive. The positive effect was especially clear after wildfires and for the abundance and diversity of Hymenoptera (bees, wasps, etc.; the main group of pollinators), while Lepidoptera (butterflies and moths) abundance showed a negative response. Short fire intervals also showed a negative effect on pollinators. In conclusion, pollinators are not only resilient to fire, but they tend to be promoted during the first postfire years. That is, fires by increasing the number of flowers, they also increase the number of flower visitors. It is also likely that this may have a positive cascading effects on other interacting species, like seed dispersers and predators. This is one of the mechanisms by which wildfires increase diversity. Pollinations is also one of the ecosystem services that fires can provide to humans [2].

 

Figure:  Weighted-mean effect sizes and 95% bias-corrected confidence intervals on abundance (closed circles) and richness (open circles) of pollinator taxa. This is for wildfire only. Sample sizes for each category are shown on the right of each effect. From [1].

References

[1] Carbone L.M., Tavella J., Pausas J.G., Aguilar R. 2019. A global synthesis of fire effects on pollinators. Global Ecology & Biogeography. [doi | pdf]

[2] Pausas J.G. & Keeley J.E. 2019. Wildfires as an ecosystem service. Frontiers in Ecology and Environment 17: 289-295. [doi | pdf | post]

Fire may disrupt plant-animal interactions. In antagonistic interactions, this disruption may benefit one of the interacting species; for instance, the reduction of a seed predator after fire can benefit the host plant [1]. The question is what happen in mutualistic interactions? Does fire disrupt mutualistic interactions generating negative consequences for the interacting species?

The Mediterranean dwarf palm Chamaerops humilis is a small dioecious palm native to the coastal shrublands of the western Mediterranean Basin. It has a specialized nursery pollination system involving the weevil Derelomus chamaeropis (Curculionidae). The plant resprouts quickly after fires (from apical buds) and produces flowers the following spring [2]. Given the specialized nursery pollination systems, this plant is a good candidate to have their pollination disrupted by fire.

In a recent study [3] we found that after fire, their pollinator (the weevil), was strongly reduced, but the fruit set remained unchanged. We documented a second beetle, a sap beetle (Meligethinus pallidulus, Nitidulidae), that were not affected by fire and acted as an effective pollinator (in a non-nursery pollination system). The temporary replacement by a sap beetle at burnt sites – an effective pollinator that had gone unnoticed until now – provided postfire reproductive resilience. That is, fire does not disrupt pollination in this specialized plant-insect system.

This is an example of the “nature’s jazz hypothesis”, i.e., species have considerable scope and capacity to adapt to each other and their environments and thereby may impart far more resilience to environmental stressors and disturbances that was once thought [4].

The dwarf palm Chamaerops humilis is well adapted to recurrent shrubland fires (i.e., of high intensity). It resprouts quickly after fire from surviving apical buds; it has rhizomes from where new stems can emerge after disturbance (I suppose this is why Humboldt mentioned this species as a social palm [2]); and its pollination is not jeopardized by fire.

The mediterranean dwarf palm Chamaerops humilis flowering (male) 2 months after fire; Valencia region, Spain (photo: JG Pausas).

References

[1] García Y., Castellanos M.C. & Pausas J.G. 2016. Fires can benefit plants by disrupting antagonistic interactions. Oecologia 182, 1165–1173. [doi | pdf | post]

[2] Postfire resprouting of Chamaerops humilis, jgpausas.blog.uv.es, 2016/03/18

[3] García, Y., Castellanos, M.C. & Pausas, J.G. 2018. Differential pollinator response underlies plant reproductive resilience after fires. Annals of Botany [doi | pdf]

[4] Schmitz, O. J. 2018. Species in ecosystems and all that jazz. – PLoS Biology 16: e2006285.

Update: paper now featured in Botany One: Plant-animal interactions deal with wildfires in unexpected ways

The winter is being quite mild untill now in eastern Iberia and almond trees are already in flower!

Almond trees (Prunus dulcis) and bumblebee (Bombus), in Calderona, Valencia, Spain, 13 Jan 2013.
“Si per la Candelaria flora, l’hivern està fora, si no flora, ni dins ni fora”
(La Candelaria és el 2 de Febrer)