Ulrich K. Schliewen’s research while affiliated with Zoologische Staatssammlung München and other places

Glossogobius, a species-rich gobiid genus with 42 recognized species distributed in the Indo-West Pacific, lacks a comprehensive phylogenetic analysis. The highest diversity of the genus occurs in the tropical West Pacific, highlighting this region as a centre of endemism. In contrast, the Indian Ocean has lower diversity (nine species). This study offers the first thorough description of Glossogobius diversity in the south-western Indian Ocean through integrative analyses. Our findings reveal nine lineages, five of which are newly identified, including a new species, Glossogobius hanisii sp. nov., described from southern Africa and Madagascar. Seven species/lineages, along with G. kokius from Mauritius and G. tenuiformis, are endemic to the south-western Indian Ocean. With 65% of Indian Ocean Glossogobius species/lineages being endemic to the south-western region, it is identified as a hotspot of endemism. The genetic structuring of these lineages along the east coast of southern Africa appears to be shaped by an interplay between life history, oceanographic conditions, and adaptations to marine biogeographic regions. Additionally, our findings highlight Madagascar’s central role in Glossogobius diversification and evolution of unique gobies, provide a framework for a comprehensive revision of Glossogobius in the region, and facilitate the identification of conservation units and the formulation of management measures.

Increasing rates of hybridization and introgression in managed populations of freshwater fish are a major threat to the long-term viability of native species. The conservation challenge begins with identifying native gene pools. For brown trout (Salmo trutta Linnaeus, 1758) in the Upper Danube drainage, this task is complicated by the presence of both naturally and anthropogenically induced admixture of highly divergent lineages (Atlantic and Danubian). Herein, a ddRADseq protocol was used to type 377 individuals from 24 populations in the Upper Danube in Austria and Germany, and from reference populations from adjacent drainages and commercial hatcheries. High genetic differentiation at small geographic scales was found among pure Danubian-lineage populations, especially in the Kalkalpen National Park (Austria). In the Upper Danube drainage of Germany, as well as in the Rhine and Elbe drainages, brown trout populations were predominantly of Atlantic-lineage origin – as were those of all commercial hatcheries. Most populations, however, showed various degrees of admixture between Danubian and Atlantic lineages, hypothesized to be the result of both natural and anthropogenic processes. We highlight the conservation value of pure Danubian-lineage populations, and the challenges promoting conservation of naturally admixed populations, while discouraging continued stocking and admixture via management activities.

Two new Kneria species, K. luansaensis sp. nov. and K. maxi sp. nov., are described from the Luansa River, a left bank tributary of the lower Luapula in the Bangweulu–Mweru ecoregion, based on an integrative approach using morphological and COI barcoding evidence. While K. luansaensis sp. nov. occurs from the source of the Luansa further downstream to above the last of the three Sanshifolo Falls, K. maxi sp. nov. only occurs downstream of all these three major falls. In Kneria, males of about ≥ 33 mm LS have an opercular and a postopercular organ. The number of lamellae on the latter seems to contain some alpha-taxonomic information, although this requires further study as allometric changes occur at about ≤ 45 mm LS. Additional external morphological characters differ between sexes, i.e., the (i) pectoral fin width (wider in males than females), (ii) dorsal fin height (longer in males than females), and (iii) length of the longest ray of the lower caudal fin lobe (longer in males than females). Agriculture, fishing with ichthyotoxines, and logging are the most pressing threats on the Luansa and thus to both the new species. Their discovery in one of the rivers of the Kundelungu Plateau and its surroundings located outside the present-day boundaries of the Kundelungu National Park highlights the need for a refined and improved protection strategy for this freshwater key biodiversity area.

The rheophilic catfishes of the Amphilius uranoscopus group (AUG) from the Congo Basin remain poorly studied. Of the 16 known species in this Amphilius group, to date, only three are described from the Congo Basin. In total 129 specimens of the AUG of the rivers of the Kundelungu Plateau and its surroundings were studied using an integrative approach combining qualitative (caudal-fin shape and colour pattern), morphological and mitochondrial DNA data (three markers: COI, CYTB and ND2). Five endemic new species, with different phylogeographic affinities, were identified. Amphilius sp. ‘luansa’ and A. sp. ‘muriel’ occur allopatrically in two adjacent rivers on the eastern flank of the plateau. Amphilius sp. ‘luansa’ is currently only known from the plateau, while A. sp. ‘muriel’ lives on and below the plateau; the latter probably due to downstream colonisation. Mitochondrial DNA data demonstrated that A. sp. ‘luansa’ belongs to the eastern-southern Africa clade, while A. sp. ‘muriel’ belongs to the Luapula-Mweru clade. Three other species, A. sp. ‘vandewalle’, A. sp. ‘luiji-bl1’ and A. sp. ‘luiji-ab-bl2’ occur on the western side of the plateau, with the last two being partially sympatric but not syntopic. Amphilius sp. ‘luiji-ab-bl2’ occurs on and below the plateau, while A. sp. ‘vandewalle’, and A. sp. ‘luiji-bl1’ only occur below the plateau. Mitochondrial DNA data showed that A. sp. ‘luiji-ab-bl2’ belongs to the Nilo-Congolian clade, while the other two species belong to the eastern-southern Africa clade. The presence of five species with three different phylogeographic affinities might, at least in part, result from the complex geological history of the Paleo-Lufira and Luapula rivers, which remained for a long time connected to the Zambezi Basin. Although considered impoverished, the plateau and its surroundings are highlighted as a centre of endemism for these rheophilic catfishes. This stresses the further need for its more effective protection.

The high diversity of extant gobiids (Gobiidae: Teleostei) makes taxonomic and phylogenetic interpretation of fossil members of the clade a difficult task. To facilitate future taxonomic and systematic work on the group, we have assembled a morphological reference database encompassing skeletal characters, an otolith atlas and otolith morphometric data of 25 present-day species from the European Gobius lineage (s.l.) that represent 18 different genera and include all nine sublineages. We show that: (1) skeletal traits and morphometric otolith variables can be diagnostic for a sublineage; (2) otolith morphology allows identification at the genus and species levels; and (3) the number of anal-fin rays and details of the otolith margins can be used to discriminate closely related dwarf gobies. The skeletal and otolith characters are largely stable in the marine gobies analysed here, whereas freshwater gobies (Padogobius, Ponto-Caspian gobies) are far more variable. This might be related to the conquest by Padogobius and Ponto-Caspian gobies of freshwater and low-salinity habitats, in which environmental conditions can fluctuate widely. We anticipate that the database presented here can be used as a valuable reference tool to assess the relationships of fossil gobiids and increase our knowledge of the evolutionary history of the group as a whole.

Didogobius lanceolatus sp. nov. is described from a single specimen collected from the southern Banc d’Arguin, Mauritania. The species differs from all currently described congeners, as well as from all species of the closely related species of the genera Chromogobius and Gammogobius, by the combination of the following characters: (1) lanceolate caudal fin; (2) small (reduced) vs. large eyes; (3) 27 vertebrae; (4) D2 I, 13, A I, 11; (5) predorsal region in front of first dorsal fin D1 naked; (6) body squamation reduced, with only few areas on flank covered by externally visible cycloid scales behind pectoral origin and on caudal peduncle; (7) anterior oculoscapular canal present, with only pores σ, κ, α, ρ; (8) posterior oculoscapular and preopercular head canal absent; (9) suborbital row 7 close to pore α with more than five papillae; (10) suborbital rows 2 and 4 close to orbit; (11) interorbital papillae absent. The new species appears most closely related to the type species of Didogobius Miller 1966, D. bentuvii Miller, 1966, as it shares a set of apparently derived morphological characters, such as the lanceolate caudal fin, minute eyes and the anterior oculoscapular canal with only pores σ, κ, α, ρ present. Phylogenetic analysis of COI-barcoding data further suggests a close relationship with two other species of the genus Didogobius exclusively sharing with the new species and D. bentuvii elevated unpaired fin ray counts, i. e., D2 branched rays ≥ 12 (vs. ≤ 11 in all other species) and A branched rays ≥ 11 (vs. ≤ 10 in all other species); these two species are D. kochi Van Tassell, 1988 and D. schlieweni Miller, 1992. Based on the description of new Didogobius species obviously closely related to the type species of Didogobius, on re-examination of the single type specimen of D. bentuvii and on the new DNA barcoding data we restrict and re-diagnose the genus Didogobius to include only the aforementioned four species. The other former Didogobius species are placed in two new genera, each unambiguously diagnosable on previously established morphological data: Marcelogobius gen. nov. with M. splechtnai, M. helenae and M. janetarum, and Peter gen. nov. with the two shrimp-associated species P. amicuscaridis and P. wirtzi.

The South Caspian Sea sub-basin, owing to its complex paleogeographic history and habitat diversity, represents a center of endemism and a high-priority conservation area for the gobiid genus Ponticola. However, very little is currently known about most biological aspects of these species in general, and this sub-basin is highly threatened by anthropogenic activities. Here we examined the phylogeographic patterns, genetic diversity, and population structure of the endemic Caspian Sea species P. gorlap, in this evolutionary distinctive and ecologically threatened Caspian sub-basin. Mitochondrial DNA control region sequences and otolith shape variations were analyzed from 472 individuals at seven South Caspian localities. Results showed: (i) two shared and eight private haplotypes, distinguished by shallow divergences, (ii) pairwise ΦST values among locations, ranging from − 0.052 to 1.00; with most of the highest between Sefidroud/Kaboudval and the other samples, (iii) genetic diversity was generally low, smaller at Kaboudval/Nekaroud, and highest at Babolroud, (iv) non-unimodal mismatch distribution and neutrality tests both rejected a recent demographic expansion scenario, (v) otolith shape analysis revealed significant differences among samples, the highest between Sefidroud/Kaboudval and the others, and (vi) Mantel tests confirmed that both pairwise ΦST and otolith shape differences were more correlated to each other than with geographic distances. Different scenarios are discussed to explain the observed patterns of genetic and otolith shape variations and population structure of P. gorlap, including possible roles of euryhalinity, and presence of migratory and resident forms.

In the welcome circumstance that species believed extinct are rediscovered, it is often the case that biological knowledge acquired before the presumed extinction is limited. Efforts to address these knowledge gaps, in particular to assess the taxonomic integrity and conservation status of such species, can be hampered by a lack of genetic data and scarcity of samples in museum collections. Here, we present a proof‐of‐concept case study based on a multidisciplinary data evaluation approach to tackle such problems. The approach was developed after the rediscovery, 40 years after its presumed extinction, of the enigmatic Lake Constance deep‐water charr Salvelinus profundus. Targeted surveys led to the capture of further species and additional sympatric normal charr, Salvelinus cf. umbla. Since the lake had been subject to massive stocking in the past, an evaluation of the genetic integrity of both extant forms was called for in order to assess possible introgression. A two‐step genomic approach was developed based on restriction site associated DNA (RAD). Diagnostic population genomic (single nucleotide polymorphism [SNP]) data were harvested from contemporary samples and used for RNA bait design to perform target capture in DNA libraries of archival scale material, enabling a comparison between extant and historic samples. Furthermore, life history traits and morphological data for both extant forms were gathered and compared with historical data from the past 60–120 years. While extant deep‐water charr matched historical deep‐water specimens in body shape, gill raker count, and growth rates, significant differences were discovered between historical and extant normal charr. These resulted were supported by genomic analyses of contemporary samples, revealing the two extant forms to be highly divergent. The results of population assignment tests suggest that the endemic deep‐water charr persisted in Lake Constance during the eutrophic phase, but not one of the historical genomic samples could be assigned to the extant normal charr taxon. Stocking with non‐endemic charr seems to be the most likely reason for these changes. This proof‐of‐concept study presents a multidisciplinary data evaluation approach that simultaneously tests population genomic integrity and addresses some of the conservation issues arising from rediscovery of a species characterized by limited data availability.

A new species, Parakneria alytogrammus, is described from the main stream of the Upper Lufira River. This species is easily distinguished from its congeners from the Congo Basin by its unique colouration, consisting of a low number of transversal bands on each of the caudal‐fin lobes, 2 (vs. 3–5) and the presence of an uninterrupted lateral mid‐longitudinal black band in fresh and preserved specimens (vs. absent). In addition, the new species differs from its Upper Lualaba congeners by the narrow width of its pectoral‐fin base, 4.8–5.6% LS [vs. wider, 8.2–10.1% for P. lufirae, 8.6% LS for P. damasi (holotype), and 7.6–7.9% LS for P. thysi]. Finally, it differs from the only species currently known from the Luapula‐Mweru system, P. malaissei, by having a short post‐dorsal distance, 36.4–36.6% LS (vs. longer, 38.6–41.1% LS) and a short post‐pelvic distance of 40.0–40.6% LS (vs. longer, 41.4–44.1% LS). Mitochondrial DNA‐haplotypes of P. alytogrammus sp. nov. form a clade, which is sister to the P. thysi clade, and from which it diverges by a genetic (Kimura 2‐parameter and uncorrected p) distance of 0.7% in the COI‐barcoding locus. The Upper Lufira, one of the sub‐basins of the Upper Congo Basin, remains poorly explored relative to its fish fauna. In contrast, the region is well explored with regard to its mineral wealth. Unfortunately, mining exploitation is carried out in the region without proper concern for the environment. Thus, the discovery of this new species for science calls for increased protection and aquatic biodiversity exploration in this mining region.

An evidence-based annotated checklist of gobiid species (Teleostei: Gobiidae) inhabiting the South Caspian Sea and its catchment area (i.e., the South Caspian Sea sub-basin) is compiled. The South Caspian Sea sub-basin gobiofauna currently comprises 38 confirmed species in 11 genera (i.e., 88.4% of the Caspian gobiofauna); the most diverse genus is Benthophilus (16 species, 42.1%), followed by Ponticola (seven species, 18.4%), and Neogobius (four species, 10.5%). Ten species (26.3%) are endemic to the South Caspian Sea sub-basin, another 21 species (55.3%) are endemic in the Caspian Sea basin as a whole, six (15.8%) are native to the Ponto-Caspian region, and one species (2.6%) is exotic. According to the current IUCN Red List, 24 species (64.9%) are listed as being of “Least Concern”, eight species (21.6%) are “Data Deficient”, and five species (13.5%) as “Not Evaluated”. Similar numbers of species are confirmed to inhabit the South Caspian Sea sub-basin waters of the three countries that border it: Iran harbors 25 species (nine genera), Azerbaijan has 28 species (10 genera), and Turkmenistan has 26 species (10 genera). The greatest known diversity of Benthophilus in South Caspian waters occurs in Azerbaijan and Turkmenistan (11 species each), whereas Iranian waters harbor seven species. In comparison, Iran, with six out of eight species (75%), has the greatest diversity of Ponticola known from the Caspian Sea basin. Species richness and endemism of the Caspian Sea gobiid-fauna varies considerably with latitude: the North, Middle and South sub-basins respectively harbor 21, 31, and 37 native species, of which 0, 3, and 10 species are endemic in that sub-basin alone. The high species diversity and endemism of Gobiidae in the South Caspian Sea sub-basin may have resulted from: (i) greater ecological diversity compared to the northern Caspian Sea marine areas (e.g., water depths) that may have led to differential niche adaptation and adaptive radiation in the Benthophilus-Anatirostrum species flock, (ii) lower historical extinction rate compared to Caspian higher latitudes, which had greater exposure to the Pleistocene’s extreme climatic changes, (iii) geological history of freshwater habitats in the South Caspian Sea sub-basin that set the speciation and evolutionary stage for the genus Ponticola during these Pleistocene climatic oscillations, (iv) presently less limiting conditions compared to the North Caspian Sea, i.e., higher present winter minimum of water temperature and higher salinity, and (v) Iranian freshwater abundance, variability and habitat diversity. Contemporary gobiid diversity and endemism in the Caspian Sea basin suggests two higher-priority conservation areas: (i) freshwater habitats of the South Caspian Sea region in Iran and Azerbaijan, and (ii) shallow coastal and deep waters of the South and Middle Caspian Sea sub-basins. An identification key is provided for the updated gobiid species from the South Caspian Sea sub-basin.