First report of the invasive golden apple snail , Pomacea canaliculata in Kenya 1 2

18 Following reports of an invasive snail causing crop damage in the expansive Mwea irrigation 19 scheme in Kenya, samples of snails and associated egg masses were collected and sent to 20 CABI laboratories in the UK for molecular identification. DNA barcoding analyses using the 21 cytochrome oxidase subunit I gene confirmed the identity of the snails as Pomacea 22 canaliculata, widely considered to be one of the most invasive invertebrates of waterways 23 and irrigation systems worldwide. To the best of our knowledge, this is the first record of P. 24 canaliculata in Kenya, and the first confirmed record of an established population in 25 continental Africa. This timely identification shows the benefit of molecular identification 26 when combined with a reliable database such as that provided by the Barcoding of Life Data 27 system. We found that the egg masses tested gave an identical barcode sequence to the 28 adult snails, allowing identifications to be made more rapidly. Given the impact of this 29 species in Asia, there is need for an assessment of the risk to Africa, and the implementation 30 of an appropriate response in Kenya and elsewhere to manage this new threat to agriculture 31 and the environment. 32

canaliculata, widely considered to be one of the most invasive invertebrates of waterways 23 and irrigation systems worldwide. To the best of our knowledge, this is the first record of P. 24 canaliculata in Kenya, and the first confirmed record of an established population in 25 continental Africa. This timely identification shows the benefit of molecular identification 26 when combined with a reliable database such as that provided by the Barcoding of Life Data 27 system. We found that the egg masses tested gave an identical barcode sequence to the 28 adult snails, allowing identifications to be made more rapidly. Given the impact of this 29 species in Asia, there is need for an assessment of the risk to Africa, and the implementation 30 of an appropriate response in Kenya  aligned using the multiple sequence alignment tools CLUSTALW (Thompson et al. 1994) 9 and MUSCLE (Edgar 2004a,b) in MEGA7 (Kumar et al. 2016) and these were then 151 optimized manually in the MEGA7 program. Evolutionary history was inferred by means of 152 the maximum likelihood method based on the Tamura-Nei model (Tamura and Nei 1993). 153 Initial tree(s) for the heuristic search were obtained automatically by applying Neighbor-Join 154 and BioNJ algorithms to a matrix of pairwise distances estimated using the maximum 155 composite likelihood (MCL) approach, before selecting the topology with superior log 156 likelihood value. Codon positions included were 1 st +2 nd +3 rd + noncoding whilst all positions 157 containing gaps and missing data were eliminated. Trees obtained were drawn to scale, with 158 branch lengths measured in the number of substitutions per site. The bootstrap consensus 159 tree was inferred from 1000 replicates and is taken to represent the evolutionary history of 160 the taxa analysed (Felsenstein 1985). Branches corresponding to partitions reproduced in 161 less than 50% of the bootstrap replicates are collapsed. The percentages of replicate trees 162 in which the associated taxa clustered together in the bootstrap test (1000 replicates) are 163 shown next to the respective branches (Felsenstein 1985).

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The four samples processed for sequencing (three adult snails plus one egg from an egg 169 mass) gave identical sequences when barcoded with the COI primers. When screened 170 against the holdings of GenBank and BOLD, all top matches, showing >99% identity to the 171 Mwea samples, were to sequences assigned to P. canaliculata with the sole exception of 172 what appeared to be an aberrant P. maculata sequence (MK992483) from Uruguay (data not 173 shown). This sequence showed in the GenBank/BLAST and BOLD results but did not 174 feature in the EMBL-EBI/FASTA top 500 results. This particular sequence also appeared 175 confounding in the phylogenetic analysis undertaken subsequently as it was placed within 176 the P. canaliculata cluster and not with the rest of P. maculata, which grouped with P. 177 insularum (Figure 3). This is to be expected given that the name Pomacea insularum was 178 formerly used as the valid name of P. maculata but is now a junior objective synonym of P. 179 maculata, following the designation of a single specimen as both the neotype of P. maculata 180 and lectotype of P. insularum; the same specimen was also designated as the neotype of P. reporting its presence in South Africa, noting that it was identified as P. lineata but was 213 probably P. canaliculata, and that it was possibly not established. 214 The arrival of this notorious invasive species in mainland Africa raises many questions that 215 cannot be dealt with in detail in this short report. One is how might it have arrived in Kenya? 216 In Asia it is thought to have been illegally but intentionally introduced to Taiwan around 1980, 217 with subsequent rapid spread to other countries in South-East Asia "predominantly human-218 mediated" (Cowie 2002), often because it was seen as a potential food source. Unconfirmed 219 media reports in Kenya suggest that the snail was introduced to control weeds, but no permit 220 to import the species has been issued by the Kenya Standing Technical Committee on 221 Imports and Exports. Having reached mainland Africa, there must also be concern that the snail will be 241 transported to other countries in the continent, including West Africa where nearly two-thirds 242 of Africa's rice is produced (Sers and Mughal 2020). Rice consumption in Africa is 243 increasing, and although the gap has been reduced, the continent is still unable to produce 244 sufficient rice to meet demand (Senthilkumar et al. 2020). No environmental suitability 245 modelling for P. canaliculata in Africa has been conducted, although models have been 246 constructed elsewhere that could be used to examine the potential spread (Gilioli et al. 247 2017). A risk assessment for P. canaliculata in Africa is needed as a priority for which such 248 modelling would be a useful input.

Consent for publication 285
Not applicable. 286

Availability of data and materials 287
The datasets used and/or analysed during the current study are available from the 288 corresponding author on reasonable request. 289

Competing interests 290
The authors declare that they have no competing interests.