Where might be many tropical insects?

Baorisa hieroglyphica  
Photo: Sanjay Sondhi
.

Global invasion history of the agricultural pest butterfly Pieris rapae revealed with genomics and citizen science

Ryan et al., 2019

 Over the last few thousand years, the seemingly inconspicuous cabbage white butterfly, Pieris rapae, has become one of the most abundant and destructive butterflies in the world. Here, we assessed variation at thousands of genetic markers from butterflies collected across 32 countries by over 150 volunteer scientists and citizens to reconstruct the global spread of this agricultural pest. Our results suggest this butterfly spread out from eastern Europe to occupy every continent except South America and Antarctica, with the timing of many of these events coinciding with human activities—migration, trade, and the development of crop cultivars that serve as food plants for the butterfly larvae. Interestingly, many of these invasions were hugely successful despite repeated losses of genetic diversity.

he small cabbage white butterfly, Pieris rapae, is a major agricultural pest of cruciferous crops and has been introduced to every continent except South America and Antarctica as a result of human activities. In an effort to reconstruct the near-global invasion history of P. rapae, we developed a citizen science project, the “Pieris Project,” and successfully amassed thousands of specimens from 32 countries worldwide. We then generated and analyzed nuclear (double-digest restriction site-associated DNA fragment procedure [ddRAD]) and mitochondrial DNA sequence data for these samples to reconstruct and compare different global invasion history scenarios. Our results bolster historical accounts of the global spread and timing of P. rapae introductions. We provide molecular evidence supporting the hypothesis that the ongoing divergence of the European and Asian subspecies of P. rapae (∼1,200 y B.P.) coincides with the diversification of brassicaceous crops and the development of human trade routes such as the Silk Route (Silk Road). The further spread of P. rapae over the last ∼160 y was facilitated by human movement and trade, resulting in an almost linear series of at least 4 founding events, with each introduced population going through a severe bottleneck and serving as the source for the next introduction. Management efforts of this agricultural pest may need to consider the current existence of multiple genetically distinct populations. Finally, the international success of the Pieris Project demonstrates the power of the public to aid scientists in collections-based research addressing important questions in invasion biology, and in ecology and evolutionary biology more broadly.

Global invasion history and patterns of genetic structure and diversity of P. rapae. (A) Genetic ancestry assignments based on the program ADMIXTURE. (B) Rooted neighbor-joining tree based on Nei’s genetic distance. (C) Among population genetic differentiation based on Weir and Cockerham’s F_ST, New Zealand and Australia are treated separately. (D) Graphical illustration of divergence scenario chosen in ABC-RF analysis. (E) Geographic representation of divergence scenario with the highest likelihood based on ABC-RF analysis; points are colored based on their population assignment using ADMIXTURE as in A, and dates represent median estimates from ABC-RF analysis. All analyses are based on 558 individuals genotyped for 17,917 ddRADseq SNPs. Explore these data further through interactive data visualizations

https://www.pnas.org/content/116/40/20015

.

.
El afecto por algo imaginado es el más fuerte de todos

Spinoza
.

Honey bees as bioindicators of changing global agricultural landscapes 
Tyler P, Quigley, Gro V Amdam and Gyan H Harwood

Agricultural landscapes are under pressure from climate change, needs for increased productivity, and changing consumer demand.

Land management decisions will affect ecologically important organisms that live on agricultural land and in surrounding areas.

Honey bees can be useful bioindicators to detect and track changes in agricultural landscape quality at spatial and temporal scales.

There is a growing need to understand relationships between agricultural intensification and global change. Monitoring solutions, however, often do not include pollinator communities that are of importance to ecosystem integrity. Here, we put forth the honey bee as an economical and broadly available bioindicator that can be used to assess and track changes in the quality of agricultural ecosystems. We detail a variety of simple, low-cost procedures that can be deployed within honey bee hives to gain generalizable information about ecosystem quality at multiple scales, and discuss the potential of the honey bee system in both environmental and ecological bioindication.

https://bit.ly/2m6VyEe
.

Landscape connectivity explains interaction network patterns at multiple scales 
Santos et al., 2019.

Under a metacommunity framework, the spatial configuration of habitat fragments could determine local community structure. Yet, quantifying fragment connectivity is challenging, as it depends on multiple variables at several geographical scales. We assessed the extent to which fragment connectivity and area explain patterns in interaction structure among four herbivore guilds and their host plants in a metacommunity. We propose an integrative connectivity metric including geographic distance, neighbouring fragment area and similarity in resource composition as an extension of Hanski's classic metric. We then used non‐linear models to assess whether fragment connectivity and area predicted link richness and similarity in link composition. We found that link richness was always negatively related to connectivity but at different geographic scales depending on the herbivore guild. In contrast, while link composition was also related to connectivity, the direction and strength of this relationship varied among herbivore guilds and type of link composition (qualitative or quantitative). Furthermore, focal fragment area was not an important determinant of interaction diversity in local communities. Our findings emphasize resource similarity as a novel dimension of fragment connectivity relevant in explaining interaction diversity patterns in natural trophic networks.

https://bit.ly/2k48IkO 
.

Caligo memnon hind wing

Maíz Azul 
Foto: https://www.foodnavigator-latam.com/

Coevolution Creates Complex Mosaics across Large Landscapes 
Fernande et al., 2019.

The spatial distribution of populations can influence the evolutionary outcome of species interactions. The variation in direction and strength of selection across local communities creates geographic selection mosaics that, when combined with gene flow and genomic processes such as genome duplication or hybridization, can fuel ongoing coevolution. A fundamental problem to solve is how coevolution proceeds when many populations that vary in their ecological outcomes are connected across large landscapes. Here we use a lattice model to explore this problem. Our results show that the complex interrelationships among the elements of the geographic mosaic of coevolution can lead to the formation of clusters of populations with similar phenotypes that are larger than expected by local selection. Our results indicate that neither the spatial distribution of phenotypes nor the spatial differences in magnitude and direction of selection alone dictate coevolutionary dynamics: the geographic mosaic of coevolution affects formation of phenotypic clusters, which in turn affect the spatial and temporal dynamics of coevolution. Because the formation of large phenotypic clusters depends on gene flow, we predict that current habitat fragmentation will change the outcomes of geographic mosaics, coupling spatial patterns in selection and phenotypes.

 https://bit.ly/2ZiBVHz
.

Utricularia gibba, a freshwater carnivorous plant 
Photo: Igor Siwanowicz
.