Quick Spreading of Populations of an Exotic Firefly throughout Spain and Their Recent Arrival in the French Pyrenees

Abstract

In August 2018, a firefly (Coleoptera: Lampyridae) of American origin was observed in several localities in Girona (Catalonia, Spain) and was described as Photinus immigrans by Zaragoza-Caballero and Vinolas, 2018. Here, we show that this species dispersed very quickly throughout northeastern Spain and was, in 2020, observed in the French Pyrenees. The animal's quick progress is documented, and part of its biology is described (dispersion speed, land use, phenology, identification of all life stages). An additional population was localized in Extremadura, and its special status is discussed. We were able to determine its Argentinian-Uruguayan origin and propose, therefore, to consider Photinus immigrans as a synonym of Photinus signaticollis (Blanchard, 1846) (=Photinus immigrans Zaragoza-Caballero and Viñolas, 2018, syn. nov.). Our data clearly show that at least the Catalan and French populations are spreading very quickly and are able to settle permanently if adequate ecosystems are found. The species is highly expansive and may well be invasive; our citizen science platforms are ideally suited to monitor their progress throughout Spain and France. This is important for avoiding future ecological problems with diverse native faunas, such as glow-worms, fireflies and earthworms. If no ways are found to stop the species' progression, the animals will quite probably invade substantial areas of France, Spain and the rest of Europe in the years to come.

Keywords: citizen science; distribution; exotic species; flight behavior; invasive; phenology.

Figure 1

Observations in northeastern (Girona), and central western Spain (Extremadura), as well as in southeastern France. (A) Overview of all European observation sites; the asterisk points to the observation in Extremadura and the question mark shows the La Rioja sightings (see below). The observation from north central Spain (La Rioja) needs further verification. (B) Visualization of the Girona and French observations. The background colors indicate the elevation (digital terrain model). Light blue lines mark rivers, whereas dark blue ovals show the main focal areas of initial Photinus sp. presence. The central black line is the French–Spanish border. (C) Time course of observations are shown as presence (pink squares) in 5 × 5 km² squares.

Figure 2

Dispersal of the Photinus firefly calculated with the nearest distance between the 2019 and 2020 records. The calculated average dispersal distance of the 2019–2020 range corresponds to 6 km/year with a SD of 3.5.

Figure 3

Comparison of Spanish (Extremaduran) and Argentinian Photinus aedeagi. Top panels: ventral, lateral and dorsal views of the aedeagi for a Spanish (S) and Argentinian specimen of P. signaticollis (A). Lower panels: semi-lateral (S) and bottom (A) views, facilitating the understanding of the aedeagus structure. Aedeagi are shown in the physiological head (up)–tail (down) orientation, as proposed by Dr. Lesley Ballantyne [26]; basal piece (a), lateral lobe (b), median lobe (c), dorsal basal projection (d)—aedeagal nomenclature following [13].

Figure 4

CORINE 2018 land cover map. The black “horizontal” line indicates the French–Spanish border.

Figure 5

South American observations. Numbers 1 to 8 indicate the Argentinian provinces where the species has been recorded (1—Buenos Aires; 2—La Pampa; 3—Río Negro; 4—Mendoza; 5—Córdoba; 6—Salta; 7—El Chaco; 8—Entre Ríos. N° 9 indicates Uruguay (source: www.inaturalist.org; www.ecoregistros.org; www.fotosaves.com.ar (all accessed 20 October 2020)).

Figure 6

Photinus signaticollis—phenology. (A): Europe (2016–2020 observations); (B): Argentina and Uruguay (2014–2020 observations); 70 records from www.inaturalist.org; www.ecoregistros.org; www.fotosaves.com.ar (accessed 20 October 2020).

Figure 7

Life stages of Photinus signaticollis. (A–D) Adult female (France), dorsal (A) and ventral view (B); adult male (France), dorsal (C) and ventral view (D). Arrows indicate the lanterns; arrowheads show the vittae (E,F). Larvae (Argentina, photo credits L.E.R.). (F) Larva (left panel) and the female (F), middle and right panel) that hatched from it. Arrow indicates the lantern. Arrowhead shows a vitta. (G) Pupae (Spain) (left—male; right—female).