Take-home: genes make the invader! ✔️ High dispersal is heritable & recessive ✔️ Fast genotypes accumulate at range edge ✔️ No microbial drivers. Understanding the success of #MermessusTrilobatus means understanding its #genetics! (work in progress - stay tuned!) 🧬🕸️ #EvolutionInAction

A two-panel boxplot comparing bacterial richness (number of observed OTUs) across spider groups. Panel a that high-dispersive spiders (left box) have lower microbial OTU richness (median ≈ 7.5) than low-dispersive spiders (right box; median ≈ 12). Panel b shows similar richness between spiders from the invasion front (Horsens; median ≈ 10.5) and those from the invasion core (Wilgartswiesen; median ≈ 9.8).

A two-panel NMDS ordination of microbial community composition (Bray–Curtis dissimilarity) for spider groups. Panel a plots high-dispersive and low-dispersive spiders; points for both overlap, indicating no distinct clustering (stress = 0.17). Panel b plots spiders from Horsens versus Wilgartswiesen; points largely overlap, showing no separation by origin (stress = 0.18).

No microbial puppet-masters here. European populations of #MermessusTrilobatus lack Rickettsia/Wolbachia; high-flyers host FEWER bacteria. Dispersal is most likely coded in genome, not microbiome. #Microbiome #Genetics doi.org/10.1007/s002...

Figure shows three side-by-side bar charts (a, b, c), each comparing the mean frequency (± SE) of a dispersal behaviour in F2 offspring across four parental breeding: HH (both parents high-dispersive), HL (high-dispersive dam, low-dispersive sire), LH (low-dispersive dam, high-dispersive sire), and LL (both parents low-dispersive). Panel (a) plots tiptoe frequency, panel (b) rafting frequency, and panel (c) take-off frequency. In each chart, the HH group bar is about three times taller than the other three bars, which are all similar in height; letters above bars (“a” for HH and “b” for HL, LH, LL) denote that HH differs significantly from the other groups, which do not differ from each other.

Dispersal isn’t random – it’s heritable! Offspring of two high-flying parents show 3× higher dispersal rates in #MermessusTrilobatus. High dispersal is recessive, helping founders race ahead then ‘dial back’ later. #Dispersal #Heritability #Evolution doi.org/10.1016/j.an...

Bar chart showing mean predation rate (± SE) of a native ground-hunting spider on two sheet-web prey. The left bar, labelled “Mermessus trilobatus (invasive)”, rises to about 70% consumed; the right bar, “Erigone dentipalpis (native)”, reaches roughly 25% consumed. Error bars illustrate standard errors, highlighting that the invader is eaten around three times more often than the native species.

Prey naïveté vs. enemy release? We pitted #MermessusTrilobatus against a native predator. Result? Invader was eaten 3× more often than local spiders 🕷️🕷️🍽️ – naïveté beats enemy-release here. #PredatorPrey #Behaviour #AlienSpecies doi.org/10.1002/ece3...

Bar chart comparing densities (individuals / m²) of eight grass-dwelling linyphiid spiders in disturbed vs. undisturbed hay meadows. For each species, two adjacent bars show mean ± SE; Mermessus trilobatus drops sharply after soil tillage (~90% decline, marked with an asterisk), whereas native species remain stable or, in Oedothorax apicatus, rise markedly. X-axis lists species; Y-axis shows individuals per square metre; significant treatment effects indicated by asterisks.

Unexpected sensitivity of #MermessusTrilobatus to soil disturbance in grasslands! Contrary to many invaders, ploughing slashes its numbers by ≈90%! ➡️ managing grasslands may rein in its spread. #Biodiversity #Disturbance @biolinvasions.bsky.social doi.org/10.1007/s105...

Two small brown spiders on their webs with white springtails. The smaller male spider is on the left, while the larger female spider on the right has a visible red mating plug that develops after her first mating to ensure paternity. Small white springtails, which serve as food for the spiders, are scattered on the silky webs.

Three stereo-microscope views of Mermessus trilobatus (dwarf spider): (a) an unmated female seen from above with a smooth epigynal, (b) a mated female showing the rounded mating plug covering her epigyne, and (c) a male with slender legs and elongated abdomen, all on a neutral background.

Tiny #spiders, huge impact! Meet #MermessusTrilobatus – a North-American dwarf spider that has stormed across #Europe in <50 yrs. We follow every silk thread of its success story 🕸️✨ Swipe through this thread for the highlights! #InvasiveSpecies #Ecology