Insects of Forensic Interest Evidence of Latitudinal and Altitudinal Shift Because the Warming Climate Changes

As previously discussed, focusing on insects, alterations in climate can affect abundance (Bale 2002; McLaughlin et al. 2002), species' distribution (Hill et al. 2002; Hughes et al. 2003; Maistrello et al. 2006; Roy andAsher 2003; Thomas et al. 2001; Warren et al. 2001), physiology (Bradshaw and Holzapfel 2001; Musolin and Numata 2003, 2004), synchrony, and relationships with hosts (Kamata et al. 2002; Visser and Holleman 2001) ultimately affecting the structure of whole communities (Harrington et al. 1999; Stenseth et al. 2002; Thomas et al. 2004; Walther et al. 2002; Wuethrich 2000). Carrion-breeding insects are displaying this phenomena with relevant consequences for the postmortem interval (PMI) evaluation as well as for other forensic deductions (e.g., evaluation of the season of death, body displacement).

To evaluate the effects of global climate change on the forensic entomological evidence evaluations, we focused our attention on the available literature and on original data collected in northern Italy in recent years. Global climate change affects the fauna of forensic importance on different scales, both structural and temporal. In fact, both the composition of the carrion community and the arrival and departure times of carrion insects are influenced by the new climatic conditions, with direct consequences for entomological evidence evaluations. In temperate regions, new species, particularly those with originally more southern distributions, have been collected during recent years from both human bodies and animal carrion or traps with meat bait used for forensic entomology experimentation (Grassberger and Frank 2004; Grassberger et al. 2003; Turchetto and Vanin 2004a, b, c; Vanin et al. 2007). Similar reports have come from both America and Europe for different zoological groups, but they are particularly important for Diptera, from a forensic entomology point of view.

The composition of carrion-breeding fauna in a region can be modified by the arrival of new species transported by humans that survive and stabilize thanks to the new climatic conditions or by spontaneous colonization. This has implications not only for the decreased value of certain species in estimating the place of death (in that they are no longer exclusive to southern regions) but also for new temporal and structural relationships in the carrion-breeding composition in a region. This is the case in which the new arrivals are not only saprophagous but also predators of other necrophagous insects.

The calliphorid Chrysomya albiceps (Diptera: Calliphoridae) is generally described as a tropical and subtropical species that can be found in Africa, southern Europe, Arabia, India, and Central and South America (Hall and Smith 1993); in recent years, however, as demonstrated by Grassberger and colleagues (Grassberger and Frank 2004; Grassberger et al. 2003), it has shifted to central Europe from the southern regions (Fig. 15.8) and in Italy from southern to northern regions (Vanin, et al. 2009). The species was recorded just recently throughout the years 1996 and 1997 by Arnaldos et al. (2001) close to the city of Murcia and by Martínez-Sánchez and coworkers (2000) in the Salamanca province. It was collected by Introna et al. (1998) in southern Italy from a partly skeletonized, decaying body during September in a suburban area of the city of Bari. Since 1999, however, it was reported also from Austria, near Vienna; from Romania near Bucharest, where C. albiceps constituted 15.6% of all trapped Calliphoridae and 11.3% of all trapped flies; from Croatia (Island of Krk); and in 1995 it was captured on a dead body in

Fig. 15.8 Shift of carrion flies to central Europe from the southern regions and to alpine valleys from the Mediterranean areas. The black arrows indicate the possible migration routes of C. albiceps; the dashed arrows indicate the migration of H. illucens and M. scalaris

an apartment in Zurich, Switzerland (Rognes 1997). Apart from some records of the French gendarmerie in 1996 (Erzinclioglu 2000), reports of C. albiceps from the Palearctic region north of the Alps were scarce. The expansion of its range to north of Paris and along the French channel coast during hot summers was probably facilitated by the mild climatic influence of the Gulf Stream (Grassberger and Frank 2004; Grassberger et al. 2003). The second and third instar larvae of this species demonstrate aggressive feeding behavior on local carrion-breeding larvae and, by eating all the early arrivals, could reset the postmortem insect clock.

Similar predatory behavior was also demonstrated by the larvae (Fig. 15.9) of the southern American black soldier fly (Hermetia illucens, Diptera: Stratiomyidae). This fly (Fig. 15.10) has been shown to be a ubiquitous inhabitant of human remains throughout the southern, central, and western United States and Hawaii. This species has also been reported from Australia and from Europe (since 1956 from Italy and doubtful from Malta in 1930) (Turchetto 2000; Venturi 1956), but in recent years it has become frequent and common in the northern region and in mountainous areas. Specimens were collected during summer in human remains in plain regions and on traps activated with meat in a Dolomitic Valley at 1330 m asl. The effect of this species on the other carrion-feeding larvae depend not only on its

Fig. 15.9 Larva of Hermetia illucens

Fig. 15.9 Larva of Hermetia

Fig. 15.10 Black soldier fly

Hermetia illucens aggressive behavior but also on its adaptability to elevation and resistance to various chemicals.

It is worth mentioning that within the zoosaprophagous Calliphoridae two new introduced species have been reported from Spain: Chrysomya mega-cephala and Protophormia terranovae (Martínez-Sánchez et al. 2007a, b; Gobbi et al. 2008; Velásquez et al. 2008). The presence of P. terranovae in Spain seem to be related to its use as commercial live bait ("asticot") (Martínez-Sánchez et al. 2007b).

The arrival or shift in new fly species involved in carrion decomposition was reported not only for flies breeding on exposed corpses but also recently for scuttle flies. These flies are able to find buried remains at different depths and are commonly found in graves. For this reason they are aptly named "coffin flies."

Megaselia scalaris (Fig. 15.11) was collected from these flies during forensic entomology experiments in a wild valley in the Alps, in both grassland and a deciduous forest. Megaselia scalaris is a polyphagous saprophage species that has been transported around the world by humans (Disney 1994). It is essentially a warm climate species and is common in the lowlands bordering the Mediterranean. In cooler climates it tends to breed in buildings or in places where it can escape frost. It has just recently been reported in Belgium and Japan (Campobasso et al. 2004). Moreover, this species has become more common in northern Italian houses and in mountainous areas, whereas until few years ago it was reported only from the central and southern regions. This is clear evidence of a northern shift of this species.

Not only new necrophagous or predatory dipterans can affect the PMI evaluation but also new fly parasitoids, particularly Hymenoptera (Fig. 15.12). As described above for the predators, parasitoids can affect the body colonization dynamics

overall in closed spaces, causing extinction of their host: the carrion breeding flies. During the summer of 2003, the presence of the Enchyrtid Tachinaephagus zaelan-dicus was reported from dipters' puparia collected from a body in an advanced state of decomposition in northern Italy (Turchetto and Vanin 2004c; Turchetto et al. 2003). This species, probably native to Australia and New Zealand, has been introduced into various parts of the world in attempts to control pest species of synanthropic diptera (Brazil, United States, Africa, and New Caledonia), but no records were available for Europe or the northern regions.

The effect of global climate change has had direct effects not only in the community composition and the extinction or arrival of new species but also in the temporal succession of the carrion breeding species regarding their abundance and phenology.

It is commonly believed that the distinct seasonal pattern of the early colonizing blowfly species allows allocation of the time of death to a particular time interval, even in cases of long PMIs, if the empty puparia of these insects can be found. The order of succession of carrion invertebrates and the arrival and departure times of taxa involved are potentially predictable (Smith 1986).

However, climate change can induce annual variations in the arrival and departure times of carrion insects (Archer 2003). Succession patterns also differ greatly between seasons, as seasonal temperature differences affect decomposition rates, which can, in turn, affect succession rates. Some carrion taxa may also be seasonally active, whereas others are active all year (Archer and Elgar 2003). Carrion taxa may also show seasonal variations in their abundance. Climate change, however, can induce annual variations in arrival and departure times of carrion insects (Archer 2003) with evident consequences in the interpretation of the entomological evidence. In fact, complications may arise from variations between the same seasons in different years, regarding both climate and the population parameters of the carrion invertebrates. In southern Europe, the phenology of several species of Calliphoridae is changing; for example, Lucilia species are active also in early spring and in late autumn, with evident widening of their activity period, Calliphora vicina specimens were found active during the winter of 2006-2007 and in 2008 Chrysomya albiceps was collected at the beginning of November in Venetian region (Vanin, unpublished).

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