Nerudia undetermined

Huber, Bernhard A., Meng, Guanliang, Král, Jiří, Ávila Herrera, Ivalú M., Izquierdo, Matias A. & Carvalho, Leonardo S., 2023, High and dry: integrative taxonomy of the Andean spider genus Nerudia (Araneae: Pholcidae), Zoological Journal of the Linnean Society 198, pp. 534-591 : 575-578

NERUDIA SP. ‘ ARG 163’

Two species were collected in La Rioja, SE Aimogasta: N. ola , and a single female specimen representing a different species. This female resembles N. rocio in having indistinct radial marks on the carapace and in having unusually long legs (tibia 1: 2.1). However, the epigynum is different ( Fig. 37B ) and resembles that of N. hoguera (and N. flecha ). The molecular data also suggest that this specimen is closer to N. hoguera than to any other sequenced species ( Fig. 2 ; Supporting Information, Fig. S4 ).

Material examined. ARGENTINA – La Rioja: • 1 ♀, in pure ethanol; SE Aimogasta, ‘site 2’; 28.9015° S, 66.6538° W; 755 m a.s.l.; under rocks; 10 Mar . 2019; B. A. Huber and M. A. Izquierdo leg.; ZFMK Arg163.

KARYOLOGY

The male karyotype of Nerudia ola is composed of 24 chromosomes. It is predominated by biarmed chromosomes ( Fig. 38A ). The prophase of the first meiotic division includes the diffuse stage. During this period, the bivalents almost decondense. In contrast to this, sex chromosomes form a highly condensed, cross-shaped element ( Fig. 38B ). A diffuse stage is also found in N. poma and Gertschiola macrostyla . The metaphase of the first meiotic division (metaphase I) consists of ten bivalents and a tetravalent formed by three X chromosomes and a Y chromosome ( Fig. 38C, D ). Within the tetravalent, each of the X chromosomes is associated by one end with the Y chromosome ( Fig. 38C ). The average size of the Y chromosome (8.3 µm, N = 3, metaphases I) is similar to the size of the X chromosomes. There are two types of metaphases of the second meiotic division (metaphase II), one with 11 chromosomes, including the Y chromosome, and the other with 13 chromosomes, including the X chromosomes ( Fig. 38E, F ). It was impossible to distinguish the sex chromosomes from the other chromosomes on the basis of their morphology or behaviour during metaphase II ( Fig. 38E, F ). One ( Fig. 39B, C ) or two chromosome pairs ( Fig. 39A ) contain a NOR. One sex chromosome also included a NOR ( Fig. 39C ), at the end involved in chromosome pairing ( Fig. 39B ).

The male karyotype of Nerudia poma consists of 26 chromosomes ( Fig. 40A ). Metaphases I contain one bivalent more than in N. ola ( Fig. 40B, C ). The structure of the sex chromosome tetravalent is the same as in N. ola ( Fig. 40B, C ) except for the smaller size of the Y chromosome (5.1 µm, N = 2, metaphases I). There are two types of metaphases II, one with 12 chromosomes, including the tiny Y chromosome, and another with 14 chromosomes, including the three X chromosomes ( Fig. 40D–F ). It was impossible to distinguish the X chromosomes from the other chromosomes at metaphase II ( Fig. 40D, F ). Metaphase II with X chromosomes is formed exclusively by biarmed chromosomes ( Fig. 41 ), which implies that all chromosome pairs and the X chromosomes are biarmed. The Y chromosome is the smallest element of metaphase II ( Fig. 40E ). Its morphology is unknown.

The male karyotype of Gertschiola macrostyla is predominated by biarmed chromosomes ( Fig. 42D ). Metaphases I contain 12 bivalents and a sex chromosome tetravalent X 1 X 2 X 3 Y. The X chromosomes are associated by the ends of both of their arms with the tiny Y chromosome, which is much smaller than in Nerudia ( Fig. 42A–C ). The average size of the Y chromosome is only 1.6 µm (N = 2, metaphases I). One chromosome pair contains a NOR. Moreover, one X chromosome has a terminal NOR ( Fig. 39D ).

SAMPLING BIAS AND BIOGEOGRAPHIC ANALYSES

The areas with high densities of records of arthropods and arachnids are poorly correlated (r = 0.391, P <0.000). In the wider area (~ 500 km) around the known geographic distribution of Nerudia , six localities stand out for their high density of records of arthropods, near the cities of Santiago, La Serena and Copiapó in Chile, and Córdoba, Cafayate and Salta in Argentina (Supporting Information, Fig. S5 ). For arachnids, only the cities of Santiago, Cafayate and Córdoba present a similar pattern, while an extra area with high density of records of Arachnida is observed near Tilcara, in northern Argentina ( Fig. 43A ). Meanwhile, the records of Nerudia are mostly located in poorly sampled regions ( Fig. 43A ), and they are not explained by the number of records of arthropods (deviance = 1.513, P = 0.2187) or by the interaction between the numbers of records of arthropods and arachnids (deviance = 2.577, P = 0.1084). However, records of Nerudia are significantly explained by the number of records of arachnids (deviance = 5.447, P = 0.019; Supporting Information, Fig. S6 ).

The species distribution modelling was based on seven principal components (PC) of the 21 predictor bioclimatic variables, which gathered 95.3% of the cumulative proportion of variance (for details, see Supporting Information, Tables S1 , S2). The first PC contributed with 43% to the Nerudia distribution modelling ( Fig. 43B ; Supporting Information, Table S3), while, the second PC contributed with 33.6% (see Table S3). Most of the areas with higher relative occurrence rates for Nerudia ( Fig. 43B ) are in the northern part of the Monte biogeographic province (sensu Morrone, 2017) (where most Nerudia records are known) and in the Atacama province in Chile and the Puna province in Bolivia (where no Nerudia or any other Ninetinae have ever been recorded).

The second principal component analysis carried out based on the extracted values for the 21 predictor bioclimatic variables for each of the Ninetinae records (Supporting Information, Table S6), resulted in eight principal components that gather 96.0% of the cumulative proportion of variance (Supporting Information, Table S4). The first PC represented 47.7% of the proportion of variance, being positively correlated with temperature seasonality and temperature annual range, but negatively correlated with annual mean temperature, minimum temperature of coldest month and mean temperature of coldest quarter (Supporting Information, Table S5; Fig. S7 ). The second PC represented 19.4% of the proportion of variance, being positively correlated with the annual precipitation and the precipitation of the driest month, of the driest quarter and of the coldest quarter, but negatively correlated with precipitation seasonality (Supporting Information, Table S5). The ordination of the Nerudia records in the multivariate space ( Fig. 44 ; Supporting Information, Fig. S7 ) indicates that this taxon is likely limited by extreme cold conditions and humid environments. Representatives of Nerudia occupy regions with lower tree density and lower tree canopy height (Supporting Information, Fig. S7 ), suggesting an association with open environments. However, such biotic and climatic conditions are not significantly different from those observed for most other Ninetinae ; the Nerudia records are within the confidence interval for other taxa ( Fig. 44 ). The environmental niche is phylogenetically conserved in the group, thus evolving as expected owing to Brownian motion (Pagel’s λ = 0.95, P -value = 0.000, for the first PC axis; full results in Supporting Information, Fig. S8 , Table S9).

Figures

Figure 2. NJ COI tree of all sequenced Nerudia and Gertschiola specimens. Species groups on the right are working hypotheses. Photo: female of Nerudia colina sp. nov. For complete tree, and for tree resulting from analysis with IQ-TREE, see Supporting Information, Figures S1, S2.

Figure 4. Nerudia colina sp. nov.; paratype male from Argentina, Jujuy, between San Salvador and Purmamarca (ZFMK Ar 23883). Left palp, prolateral (A) and retrolateral (B) views. Abbreviations: b, genital bulb; c, coxa; e, embolus; f, femur; p, procursus; pa, patella; ta, tarsus; ti, tibia; tr, trochanter; va, ventral apophysis. Scale line: 0.3 mm.

Figure 5. Nerudia colina sp. nov.; paratype male and paratype female from Argentina, Jujuy, between San Salvador and Purmamarca (ZFMK Ar 23883).A–C, left male palpal tarsus and procursus, prolateral, dorsal, and retrolateral views (arrow points at distinctive subdistal sclerite). D–F, left male genital bulb, prolateral, dorsal, and retrolateral views. G, H, male chelicerae, frontal and lateral views. I, cleared female genitalia, dorsal view. Abbreviations: e, embolus; r, ‘receptacle’; va, ventral apophysis. Scale lines: 0.2 mm.

Figure 6. Nerudia colina sp. nov.; paratype female from Argentina, Jujuy, between San Salvador and Purmamarca (ZFMK Ar 23883). A, abdomen and epigynum, ventral view. B, median structures in internal genitalia. C, D, cleared genitalia, ventral and dorsal views. Scale lines: 0.2 mm (A, C, D), 0.1 mm (B).

Figure 7. Nerudia colina sp. nov.; male and female from Argentina, Jujuy, between San Salvador and Purmamarca (ZFMK Ar 23883 and ZFMK Arg178). A, male clypeus and chelicerae, frontal view (arrows point at indentations for genital bulb at rest). B, female prosoma, frontal view. C, left male chelicera, frontal view. D, female chelicerae and right palp, proximal segments, lateral view. E, male palpal tarsal organ. F, female tarsal organ on tarsus 1. Scale lines: 20 µm (A), 100 µm (B, D), 10 µm (C), 2 µm (E, F).

Figure 8. Nerudia colina sp. nov.; male and female from Argentina, Jujuy, between San Salvador and Purmamarca (ZFMK Ar 23883 and ZFMK Arg178). A, detail of male left tibia 1, prolateral view. B, hairs on male tibia 1. C, female palpal tibia, dorsal view. D, female left tarsus 4, prolateral view (arrow points at comb-hair). E, F, female ALS. Scale lines: 20 µm (A), 10 µm (B–F).

Figure 37. Epigyna of two formally undescribed putative species, ventral views. A, Nerudia ‘Arg23a’ from Argentina, San Juan, 35 km W Las Flores (ZFMK Ar 23911). B, N. ‘Arg163’ from Argentina, La Rioja, SE Aimogasta, ‘site 2’ (ZFMK Arg163). Scale lines: 0.2 mm.

Figure 38. Nerudia ola sp. nov.; male chromosome plates. Panels C, D contain a scheme of the sex chromosome multivalent (blue – X chromosomes, orange – Y chromosome). A, mitotic metaphase, 2n = 24. Note the predomination of biarmed chromosomes. B, diffuse stage. Note the cross-shaped multivalent consisting of four sex chromosomes. The multivalent exhibits positive heteropycnosis.C, D, metaphases I consisting of ten bivalents and a sex chromosome multivalent comprising three X chromosomes and a Y chromosome. Multivalent delimited by dotted line. One X chromosome is not included in the multivalent at D. E, early metaphase II containing the X chromosomes (n = 13). It is impossible to distinguish the X chromosomes from other chromosomes. F, early metaphase II containing the Y chromosome (n = 11). It is impossible to distinguish the Y chromosome from other chromosomes. Abbreviations: m, sex chromosome multivalent; X, X chromosome; Y, Y chromosome. Scale lines: 10 µm.

Figure 39. Nerudia ola sp. nov. (A–C) and Gertschiola macrostyla (D); male meiosis, detection of nucleolus organizer regions (NORs; red signals). Chromosomes counterstained with DAPI (blue). Panels B–D contain schemes of the sex chromosome multivalents. A, diffuse stage. Sex chromosome body and two decondensed bivalents exhibit a signal. B, metaphase I, one bivalent includes a NOR. Another NOR is at the end of a sex chromosome involved in pairing. C, metaphase I, sex chromosome multivalent collapsed. One bivalent and one end of a sex chromosome bear a NOR. D, metaphase I. One bivalent and one end of an X chromosome contains a NOR. Note the sex chromosome multivalent in the upper left corner of the panel. Symbols: arrow, NOR-bearing bivalent; arrowhead, sex chromosome body (A), sex chromosome multivalent (B, D) or particular sex chromosomes (C, numbered). Abbreviations: m, sex chromosome multivalent; SCB, sex chromosome body; X, X chromosome; Y, Y chromosome. Scale lines: 10 µm.

Figure 40. Nerudia poma sp. nov., male chromosome plates. Panels B, C contain a scheme of the sex chromosome multivalent (blue – X chromosomes, orange – Y chromosome). A, mitotic metaphase, 2n = 26. Note the predomination of biarmed chromosomes. The Y chromosome is the smallest element of the complement. B, C, metaphases I consisting of 11 bivalents and a sex chromosome multivalent comprising three X chromosomes and a Y chromosome. Multivalent delimited by dotted line. D, metaphase II containing X chromosomes (n = 14). It is impossible to distinguish the X chromosomes from other chromosomes. E, early metaphase II containing the Y chromosome (n = 12). The Y chromosome is the smallest chromosome of the plate. F, late metaphase II containing the X chromosomes (n = 14). Note the predomination of biarmed chromosomes. This plate was used to construct the haploid karyotype of the species (Fig. 41). Abbreviations: m, sex chromosome multivalent; X, X chromosome; Y, Y chromosome. Scale lines: 10 µm.

Figure 41. Nerudia poma sp. nov., haploid karyotype (n = 14) based on metaphase II containing X chromosomes. It consists of nine metacentric (nos 1–8, 10) and five submetacentric chromosomes (nos 9, 11–14). It is impossible to distinguish X chromosomes on the basis of their morphology or behaviour. Scale line: 10 µm.

Figure 42. Gertschiola macrostyla sp. nov.; male chromosome plates. Panels A–C contain a scheme of the sex chromosome multivalent (blue – X chromosomes,orange – Ychromosome,black knob – supposedcentromere).A–C,metaphases I consisting of 12 bivalents and a sex chromosome multivalent comprising three X chromosomes and a Y chromosome. Multivalent delimited by dotted line. D, plate composed of two sister metaphases II. Note the tiny Y chromosome. Abbreviations: m, sex chromosome multivalent; X, X chromosome; Y, Y chromosome. Scale lines: 10 µm.

Figure 43. A, density of records of arachnids surrounding the geographic distribution of Nerudia representatives, with numbered high density regions (reddish areas: 1. Santiago; 2. Córdoba; 3. Cafayate; 4. Tilcara). Dotted line represents 500 km buffer around Nerudia records (black dots). Note that Nerudia records are concentrated in poorly sampled regions (bluish areas). B, relative occurrence rate (ROR) of Nerudia species, with numbered biogeographic regions. Polygons represent the biogeographical regionalisation (sensu Morrone, 2017) in the Andean (5) and Neotropical (6–12) regions. Neotropical provinces: (6) Prepuna; (7) Monte; (8) Pampean; (9) Chaco; (10) Yungas; (11) Puna; and (12) Atacama. The reddish areas denote regions where Nerudia is expected to occur; in some of these, no Ninetinae have ever been recorded: the Atacama province in Chile and the Puna province in Bolivia.

Figure 44. Principal component analysis of the environmental conditions for Nerudia representatives (red circles and ellipse) and other Ninetinae (black triangles and dotted line ellipse). The ellipses encompass the values within a 95% confidence interval of a multivariate t-distribution. Darker symbols result from superimposition. Note that the environmental conditions for Nerudia representatives are within the confidence interval for other ninetines, suggesting that the environmental niche of Nerudia is not significantly different from other Ninetinae taxa.